diff --git a/src/vim9compile.c b/src/vim9compile.c
index 7ae47b3..58f4db9 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -1460,7 +1460,7 @@
     isn_T	*isn;
     garray_T	*stack = &cctx->ctx_type_stack;
     int		argoff;
-    type_T	**argtypes;
+    type_T	**argtypes = NULL;
 
     RETURN_OK_IF_SKIP(cctx);
     argoff = check_internal_func(func_idx, argcount);