diff --git a/src/sfnt/ttload.c b/src/sfnt/ttload.c
index 5c00b09fd..e07e39279 100644
--- a/src/sfnt/ttload.c
+++ b/src/sfnt/ttload.c
@@ -939,6 +939,9 @@
             /* invalid entry; ignore it */
             entry->stringLength = 0;
           }
+
+          /* mark the string as not yet loaded */
+          entry->string = NULL;
         }
       }