diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c
index c876a84719e..7c346e6ce7c 100644
--- a/src/backend/storage/ipc/dsm_impl.c
+++ b/src/backend/storage/ipc/dsm_impl.c
@@ -214,7 +214,7 @@ dsm_impl_can_resize(void)
 		case DSM_IMPL_WINDOWS:
 			return false;
 		case DSM_IMPL_MMAP:
-			return false;
+			return true;
 		default:
 			return false;		/* should not happen */
 	}