diff --git a/src/vim9class.c b/src/vim9class.c
index c3ccf02..e847bf0 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -4054,6 +4054,7 @@
 	vim_free(ga.ga_data);
 	return NULL;
     }
+    ga_append(&ga, NUL);
     return (char_u *)ga.ga_data;
 }