diff --git a/src/util/virstoragefile.c b/src/util/virstoragefile.c
index ca5cbb4eeb..3da9073dff 100644
--- a/src/util/virstoragefile.c
+++ b/src/util/virstoragefile.c
@@ -955,6 +955,10 @@ virStorageFileGetMetadataFromBuf(const char *path,
                                  int *backingFormat)
 {
     virStorageSourcePtr ret = NULL;
+    int dummy;
+
+    if (!backingFormat)
+        backingFormat = &dummy;
 
     if (!(ret = virStorageFileMetadataNew(path, format)))
         return NULL;
diff --git a/src/util/virstoragefile.h b/src/util/virstoragefile.h
index d08aea172d..0ba746ab7d 100644
--- a/src/util/virstoragefile.h
+++ b/src/util/virstoragefile.h
@@ -301,8 +301,7 @@ virStorageSourcePtr virStorageFileGetMetadataFromBuf(const char *path,
                                                      size_t len,
                                                      int format,
                                                      int *backingFormat)
-    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2) ATTRIBUTE_NONNULL(4)
-    ATTRIBUTE_NONNULL(5);
+    ATTRIBUTE_NONNULL(1) ATTRIBUTE_NONNULL(2);
 int virStorageFileChainGetBroken(virStorageSourcePtr chain,
                                  char **broken_file);