diff --git a/src/_macosx.m b/src/_macosx.m
index c0bd68f9c881..8f1412a99b3b 100644
--- a/src/_macosx.m
+++ b/src/_macosx.m
@@ -6049,7 +6049,9 @@ - (int)index
         [window orderFront:nil];
     }
     [pool release];
+    Py_BEGIN_ALLOW_THREADS
     [NSApp run];
+    Py_END_ALLOW_THREADS
     Py_INCREF(Py_None);
     return Py_None;
 }