diff --git a/Python/ceval.c b/Python/ceval.c
index 1af998d..b6501b3 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1997,7 +1997,7 @@
 			break;
 
 		case BUILD_MAP:
-			x = PyDict_New();
+			x = _PyDict_NewPresized((Py_ssize_t)oparg);
 			PUSH(x);
 			if (x != NULL) continue;
 			break;