diff --git a/src/hb-wasm-api-blob.hh b/src/hb-wasm-api-blob.hh
index e9aff8968..fbff0ff1f 100644
--- a/src/hb-wasm-api-blob.hh
+++ b/src/hb-wasm-api-blob.hh
@@ -40,6 +40,9 @@ blob_free (HB_WASM_EXEC_ENV
     return;
 
   module_free (blob->data);
+
+  blob->data = nullref;
+  blob->length = 0;
 }
 
 
diff --git a/src/hb-wasm-api-buffer.hh b/src/hb-wasm-api-buffer.hh
index 949195167..07d7ab418 100644
--- a/src/hb-wasm-api-buffer.hh
+++ b/src/hb-wasm-api-buffer.hh
@@ -43,6 +43,10 @@ buffer_contents_free (HB_WASM_EXEC_ENV
 
   module_free (contents->info);
   module_free (contents->pos);
+
+  contents->info = nullref;
+  contents->pos = nullref;
+  contents->length = 0;
 }
 
 void