diff --git a/build.py b/build.py
index 9037cd9e78e..15c07e8823b 100755
--- a/build.py
+++ b/build.py
@@ -116,6 +116,10 @@ def choose_omero_version():
     args = list(sys.argv)
     args.pop(0)
 
+    # Unset CLASSPATH, since this breaks the build
+    if os.environ.get('CLASSPATH'):
+        del os.environ['CLASSPATH']
+
     try:
         if len(args) > 0 and args[0] == "-perf":
             args.pop(0)