diff --git a/IPython/core/compilerop.py b/IPython/core/compilerop.py
index e39ded6..f529eb5 100644
--- a/IPython/core/compilerop.py
+++ b/IPython/core/compilerop.py
@@ -56,7 +56,7 @@ def code_name(code, number=0):
     
     This now expects code to be unicode.
     """
-    hash_digest = hashlib.md5(code.encode("utf-8")).hexdigest()
+    hash_digest = hashlib.sha1(code.encode("utf-8")).hexdigest()
     # Include the number and 12 characters of the hash in the name.  It's
     # pretty much impossible that in a single session we'll have collisions
     # even with truncated hashes, and the full one makes tracebacks too long