diff --git a/lang/compile.py b/lang/compile.py
index fdf61e2..d80e9f0 100755
--- a/lang/compile.py
+++ b/lang/compile.py
@@ -281,6 +281,9 @@
 		if line[5] != "Args" or len(args) == 0:
 			print("no function args? line: %s" % (' '.join(line)))
 			return (None, [])
+		if len(set(args)) < len(args):
+			print("duplicate function args? line: %s" % (' '.join(line)))
+			return (None, [])
 	else:
 		args = []
 	while len(lines) != 0: