diff --git a/CHANGES b/CHANGES
index 229b114c..570eb46d 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2,6 +2,7 @@
 
 gcf 2.11:
  * Remove bogus check for rspec tag (#885)
+ * Properly remove prefix from signature refid in SFA credentials. (#890)
 
 gcf 2.10:
  * Changed references to trac.gpolab.bbn.com to point to Github.
diff --git a/agg_nick_cache.base b/agg_nick_cache.base
index df99e67b..c536c7fb 100644
--- a/agg_nick_cache.base
+++ b/agg_nick_cache.base
@@ -721,3 +721,25 @@ ukl-og3=urn:publicid:IDN+glab077.e4.ukl.german-lab.de:gcf+authority+am,https://g
 kaiserslautern-og=urn:publicid:IDN+glab077.e4.ukl.german-lab.de:gcf+authority+am,https://glab077.e4.ukl.german-lab.de:5002
 kaiserslautern-og2=urn:publicid:IDN+glab077.e4.ukl.german-lab.de:gcf+authority+am,https://glab077.e4.ukl.german-lab.de:5002
 kaiserslautern-og3=urn:publicid:IDN+glab077.e4.ukl.german-lab.de:gcf+authority+am,https://glab077.e4.ukl.german-lab.de:5001
+
+# =====
+# University of Michigan InstaGENI
+# =====
+umich-ig=urn:publicid:IDN+instageni.research.umich.edu+authority+cm,https://instageni.research.umich.edu:12369/protogeni/xmlrpc/am/2.0
+umich-ig1=urn:publicid:IDN+instageni.research.umich.edu+authority+cm,https://instageni.research.umich.edu:12369/protogeni/xmlrpc/am/1.0
+umich-ig2=urn:publicid:IDN+instageni.research.umich.edu+authority+cm,https://instageni.research.umich.edu:12369/protogeni/xmlrpc/am/2.0
+umich-ig3=urn:publicid:IDN+instageni.research.umich.edu+authority+cm,https://instageni.research.umich.edu:12369/protogeni/xmlrpc/am/3.0
+umich-ig-of=urn:publicid:IDN+openflow:foam:foam.instageni.research.umich.edu+authority+am,https://foam.instageni.research.umich.edu:3626/foam/gapi/2
+umich-ig-of1=urn:publicid:IDN+openflow:foam:foam.instageni.research.umich.edu+authority+am,https://foam.instageni.research.umich.edu:3626/foam/gapi/1
+umich-ig-of2=urn:publicid:IDN+openflow:foam:foam.instageni.research.umich.edu+authority+am,https://foam.instageni.research.umich.edu:3626/foam/gapi/2
+
+# =====
+# University of Kentucky MCV InstaGENI
+# =====
+ukymcv-ig=urn:publicid:IDN+mcv.sdn.uky.edu+authority+cm,https://mcv.sdn.uky.edu:12369/protogeni/xmlrpc/am/2.0
+ukymcv-ig1=urn:publicid:IDN+mcv.sdn.uky.edu+authority+cm,https://mcv.sdn.uky.edu:12369/protogeni/xmlrpc/am/1.0
+ukymcv-ig2=urn:publicid:IDN+mcv.sdn.uky.edu+authority+cm,https://mcv.sdn.uky.edu:12369/protogeni/xmlrpc/am/2.0
+ukymcv-ig3=urn:publicid:IDN+mcv.sdn.uky.edu+authority+cm,https://mcv.sdn.uky.edu:12369/protogeni/xmlrpc/am/3.0
+ukymcv-ig-of=urn:publicid:IDN+openflow:foam:foam.mcv.sdn.uky.edu+authority+am,https://foam.mcv.sdn.uky.edu:3626/foam/gapi/2
+ukymcv-ig-of1=urn:publicid:IDN+openflow:foam:foam.mcv.sdn.uky.edu+authority+am,https://foam.mcv.sdn.uky.edu:3626/foam/gapi/1
+ukymcv-ig-of2=urn:publicid:IDN+openflow:foam:foam.mcv.sdn.uky.edu+authority+am,https://foam.mcv.sdn.uky.edu:3626/foam/gapi/2
diff --git a/src/gcf/sfa/trust/credential.py b/src/gcf/sfa/trust/credential.py
index 046170e4..5fb4604e 100644
--- a/src/gcf/sfa/trust/credential.py
+++ b/src/gcf/sfa/trust/credential.py
@@ -183,20 +183,26 @@ def set_issuer_gid(self, gid):
         self.gid = gid
 
     def decode(self):
+        # Helper function to pull characters off the front of a string if present
+        def remove_prefix(text, prefix):
+            if text and prefix and text.startswith(prefix):
+                return text[len(prefix):]
+            return text
+
         try:
             doc = parseString(self.xml)
         except ExpatError,e:
             logger.log_exc ("Failed to parse credential, %s"%self.xml)
             raise
         sig = doc.getElementsByTagName("Signature")[0]
-        ref_id = sig.getAttribute("xml:id").strip().replace("Sig_","",1)
+        ref_id = remove_prefix(sig.getAttribute("xml:id").strip(), "Sig_")
         # The xml:id tag is optional, and could be in a 
         # Reference xml:id or Reference UID sub element instead
         if not ref_id or ref_id == '':
             reference = sig.getElementsByTagName('Reference')[0]
-            ref_id = reference.getAttribute('xml:id').strip().strip('Sig_')
+            ref_id = remove_prefix(reference.getAttribute('xml:id').strip(), 'Sig_')
             if not ref_id or ref_id == '':
-                ref_id = reference.getAttribute('URI').strip().strip('#')
+                ref_id = remove_prefix(reference.getAttribute('URI').strip(), '#')
         self.set_refid(ref_id)
         keyinfos = sig.getElementsByTagName("X509Data")
         gids = None