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;
diff --git a/Python/compile.c b/Python/compile.c
index 3b0c53f..36ad8a4 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -2922,11 +2922,9 @@
 	case IfExp_kind:
 		return compiler_ifexp(c, e);
 	case Dict_kind:
-		/* XXX get rid of arg? */
-		ADDOP_I(c, BUILD_MAP, 0);
 		n = asdl_seq_LEN(e->v.Dict.values);
-		/* We must arrange things just right for STORE_SUBSCR.
-		   It wants the stack to look like (value) (dict) (key) */
+		ADDOP_I(c, BUILD_MAP, (n>255 ? 255 : n));
+		n = asdl_seq_LEN(e->v.Dict.values);
 		for (i = 0; i < n; i++) {
 			VISIT(c, expr, 
 				(expr_ty)asdl_seq_GET(e->v.Dict.values, i));