diff --git a/omnivore/tasks/jumpman/jumpman_editor.py b/omnivore/tasks/jumpman/jumpman_editor.py
index 0da8ba28..7357446d 100644
--- a/omnivore/tasks/jumpman/jumpman_editor.py
+++ b/omnivore/tasks/jumpman/jumpman_editor.py
@@ -388,6 +388,10 @@ def compile_assembly_source(self, show_info=False):
             except SyntaxError, e:
                 log.error("Assembly error: %s" % e.msg)
                 self.window.error(e.msg, "Assembly Error")
+            except ImportError:
+                log.error("Please install pyatasm to compile custom code.")
+                self.assembly_source = ""
+                self.old_trigger_mapping = dict()
             self.update_trigger_mapping()
             if show_info:
                 dlg = wx.lib.dialogs.ScrolledMessageDialog(self.window.control, self.custom_code.info, "Assembly Results")
diff --git a/omnivore/utils/jumpman.py b/omnivore/utils/jumpman.py
index f9707380..c424191a 100644
--- a/omnivore/utils/jumpman.py
+++ b/omnivore/utils/jumpman.py
@@ -1,7 +1,5 @@
 import numpy as np
 
-from pyatasm import Assemble
-
 from atrcopy import selected_bit_mask, match_bit_mask, data_bit_mask, comment_bit_mask
 
 from omnivore.utils.runtime import get_all_subclasses
@@ -995,6 +993,8 @@ class JumpmanCustomCode(object):
     std_gameloop = [ord(x) for x in " \xd0I \x00K\xad>(\xc9\x00\xf0\x11\xad\xbe0\xc9\x08\x90\xef\xad\xf00\xc9\xff\xd0\xe5L?(lD("]
 
     def __init__(self, filename):
+        # raise ImportError and let caller handle it
+        from pyatasm import Assemble
         asm = Assemble(filename)
         if not asm:
             raise SyntaxError(asm.errors)