diff --git a/basico/model_io.py b/basico/model_io.py
index 19187bc..88a452d 100644
--- a/basico/model_io.py
+++ b/basico/model_io.py
@@ -233,10 +233,10 @@ def load_model_from_string(content):
     if type(content) is bytes:
         content = content.decode("utf8")
 
-    if '<COPASI ' in content and model.loadModelFromString(content, os.getcwd()):
+    if '<sbml ' in content and model.importSBMLFromString(content):
         return set_current_model(model)
 
-    if '<sbml ' in content and model.importSBMLFromString(content):
+    if '<COPASI ' in content and model.loadModelFromString(content, os.getcwd()):
         return set_current_model(model)
 
     if '<sedML '  in content and model.importSEDMLFromString(content):
@@ -332,7 +332,7 @@ def remove_annotations(content, annotations):
         for annotation in root.iter('{%s}%s' % (namespace, element)):
             annotation.getparent().remove(annotation)
 
-    return etree.tostring(root, pretty_print=True).decode('utf-8')
+    return etree.tostring(root, pretty_print=True, xml_declaration=True, encoding="UTF-8").decode('utf-8')
 
 
 def load_model(location, remove_user_defined_functions=False):
diff --git a/tests/test_basico_io.py b/tests/test_basico_io.py
index 5f0f7f2..3796508 100644
--- a/tests/test_basico_io.py
+++ b/tests/test_basico_io.py
@@ -163,7 +163,26 @@ def test_import_sbml_with_pre_processing(self):
         
         basico.remove_datamodel(dm)
 
+    @unittest.skipUnless(_have_lxml, "lxml not available")
+    def test_import_sbml_with_pre_processing(self):
+        filename = os.path.join(os.path.dirname(__file__), 'test_data', 'import_sbml_issue.xml')
+        self.assertTrue(os.path.exists(filename))
 
+        # this file contains special processing instructions 
+        # since an initial value is used in an expression. 
+
+        dm = basico.import_sbml(filename, annotations_to_remove=[
+            ('initialValue', 'http://copasi.org/initialValue')],
+            ensure_unique_names=True
+        )
+
+        self.assertTrue(dm is not None)
+        species = basico.as_dict(basico.get_species())
+        self.assertEqual(len(species), 13)
+        params = basico.as_dict(basico.get_parameters())
+        self.assertEqual(len(params), 7)
+        
+        basico.remove_datamodel(dm)
 
 
 if __name__ == "__main__":
diff --git a/tests/test_data/import_sbml_issue.xml b/tests/test_data/import_sbml_issue.xml
new file mode 100644
index 0000000..fff98c6
--- /dev/null
+++ b/tests/test_data/import_sbml_issue.xml
@@ -0,0 +1,521 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Created by COPASI version 4.12 (Build 81) on 2014-07-22 13:01 with libSBML version 5.9.0. -->
+<sbml xmlns="http://www.sbml.org/sbml/level2/version4" level="2" version="4">
+  <model metaid="COPASI0" id="New_Model" name="New Model">
+    <annotation>
+      <COPASI xmlns="http://www.copasi.org/static/sbml">
+        <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+          <rdf:Description rdf:about="#COPASI0">
+            <dcterms:created>
+              <rdf:Description>
+                <dcterms:W3CDTF>2014-07-22T10:40:24Z</dcterms:W3CDTF>
+              </rdf:Description>
+            </dcterms:created>
+          </rdf:Description>
+        </rdf:RDF>
+      </COPASI>
+    </annotation>
+    <listOfUnitDefinitions>
+      <unitDefinition id="volume" name="volume">
+        <listOfUnits>
+          <unit kind="litre" exponent="1" scale="-3" multiplier="1"/>
+        </listOfUnits>
+      </unitDefinition>
+      <unitDefinition id="time" name="time">
+        <listOfUnits>
+          <unit kind="second" exponent="1" scale="0" multiplier="86400"/>
+        </listOfUnits>
+      </unitDefinition>
+      <unitDefinition id="substance" name="substance">
+        <listOfUnits>
+          <unit kind="mole" exponent="1" scale="-3" multiplier="1"/>
+        </listOfUnits>
+      </unitDefinition>
+    </listOfUnitDefinitions>
+    <listOfCompartments>
+      <compartment id="cell" name="cell" spatialDimensions="3" size="1" constant="true"/>
+    </listOfCompartments>
+    <listOfSpecies>
+      <species metaid="COPASI1" id="RCT0" name="RCT0" compartment="cell" initialConcentration="76" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI1">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T10:49:00Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI2" id="alpha" name="alpha" compartment="cell" initialConcentration="11" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI2">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T10:48:59Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI3" id="BN1" name="BN1" compartment="cell" initialConcentration="13" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI3">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:24:46Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI4" id="BN2" name="BN2" compartment="cell" initialConcentration="0" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI4">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:27:14Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI5" id="BN3" name="BN3" compartment="cell" initialConcentration="0" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI5">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:28:55Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI6" id="BN4" name="BN4" compartment="cell" initialConcentration="0" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI6">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:16:49Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI7" id="BTX" name="BTX" compartment="cell" initialConcentration="0" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI7">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:32:52Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI8" id="BM" name="BM" compartment="cell" initialConcentration="0" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI8">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:23:53Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI9" id="RCT1" name="RCT1" compartment="cell" initialConcentration="0" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI9">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:40:19Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI10" id="RC" name="RC" compartment="cell" initialConcentration="76" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI10">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:15:55Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI11" id="beta" name="beta" compartment="cell" initialConcentration="13" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI11">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:17:28Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI12" id="BN5" name="BN5" compartment="cell" initialConcentration="0" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI12">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:54:12Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+      <species metaid="COPASI13" id="BN6" name="BN6" compartment="cell" initialConcentration="0" hasOnlySubstanceUnits="false" boundaryCondition="true" constant="false">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI13">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:56:00Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </species>
+    </listOfSpecies>
+    <listOfParameters>
+      <parameter id="k0" name="k0" value="0.0154" constant="true"/>
+      <parameter metaid="COPASI14" id="k1" name="k1" value="0.0318" constant="true">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI14">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:11:50Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </parameter>
+      <parameter metaid="COPASI15" id="k2" name="k2" value="0.0282" constant="true">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI15">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:11:47Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </parameter>
+      <parameter id="k3" name="k3" value="0.0565" constant="true"/>
+      <parameter id="k4" name="k4" value="0.52" constant="true"/>
+      <parameter metaid="COPASI16" id="q" name="q" value="2" constant="true">
+        <annotation>
+          <COPASI xmlns="http://www.copasi.org/static/sbml">
+            <rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
+              <rdf:Description rdf:about="#COPASI16">
+                <dcterms:created>
+                  <rdf:Description>
+                    <dcterms:W3CDTF>2014-07-22T11:12:13Z</dcterms:W3CDTF>
+                  </rdf:Description>
+                </dcterms:created>
+              </rdf:Description>
+            </rdf:RDF>
+          </COPASI>
+        </annotation>
+      </parameter>
+      <parameter id="epsilon" name="epsilon" value="0" constant="true"/>
+    </listOfParameters>
+    <listOfRules>
+      <assignmentRule variable="RC">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <plus/>
+            <ci> RCT0 </ci>
+            <ci> RCT1 </ci>
+          </apply>
+        </math>
+      </assignmentRule>
+      <assignmentRule variable="beta">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <plus/>
+            <ci> BM </ci>
+            <ci> BN1 </ci>
+            <ci> BN2 </ci>
+            <ci> BN3 </ci>
+            <ci> BN4 </ci>
+            <ci> BN5 </ci>
+            <ci> BN6 </ci>
+            <ci> BTX </ci>
+          </apply>
+        </math>
+      </assignmentRule>
+      <rateRule variable="RCT0">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <apply>
+                <minus/>
+                <ci> k0 </ci>
+              </apply>
+              <apply>
+                <plus/>
+                <ci> epsilon </ci>
+                <ci> BM </ci>
+              </apply>
+              <ci> RCT0 </ci>
+            </apply>
+            <apply>
+              <times/>
+              <ci> k1 </ci>
+              <ci> BTX </ci>
+              <ci> RCT0 </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="alpha">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <ci> k1 </ci>
+              <ci> BTX </ci>
+              <ci> RCT0 </ci>
+            </apply>
+            <apply>
+              <times/>
+              <ci> k2 </ci>
+              <apply>
+                <power/>
+                <ci> BTX </ci>
+                <ci> q </ci>
+              </apply>
+              <ci> alpha </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="BN1">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <ci> k2 </ci>
+              <apply>
+                <power/>
+                <ci> BTX </ci>
+                <ci> q </ci>
+              </apply>
+              <ci> alpha </ci>
+            </apply>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN1 </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="BN2">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN1 </ci>
+            </apply>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN2 </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="BN3">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN2 </ci>
+            </apply>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN3 </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="BN4">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN3 </ci>
+            </apply>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN4 </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="BTX">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN6 </ci>
+            </apply>
+            <apply>
+              <times/>
+              <ci> k4 </ci>
+              <ci> BTX </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="BM">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <times/>
+            <ci> k4 </ci>
+            <ci> BTX </ci>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="RCT1">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <times/>
+            <ci> k0 </ci>
+            <apply>
+              <plus/>
+              <ci> epsilon </ci>
+              <ci> BM </ci>
+            </apply>
+            <ci> RCT0 </ci>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="BN5">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN4 </ci>
+            </apply>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN5 </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+      <rateRule variable="BN6">
+        <math xmlns="http://www.w3.org/1998/Math/MathML">
+          <apply>
+            <minus/>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN5 </ci>
+            </apply>
+            <apply>
+              <times/>
+              <cn> 6 </cn>
+              <ci> k3 </ci>
+              <ci> BN6 </ci>
+            </apply>
+          </apply>
+        </math>
+      </rateRule>
+    </listOfRules>
+  </model>
+</sbml>