1 files changed, 1 insertions, 1 deletions
diff --git a/Python/compile.c b/Python/compile.c
index b246c3b..a6884ec 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -985,7 +985,7 @@ PyCompile_OpcodeStackEffect(int opcode, int oparg)
         case BUILD_MAP_UNPACK_WITH_CALL:
             return 1 - (oparg & 0xFF);
         case BUILD_MAP:
-            return 1;
+            return 1 - 2*oparg;
         case LOAD_ATTR:
             return 0;
         case COMPARE_OP: