diff --git a/src/sfnt/ttload.c b/src/sfnt/ttload.c
index 4c0595859..9d52fca3a 100644
--- a/src/sfnt/ttload.c
+++ b/src/sfnt/ttload.c
@@ -340,6 +340,9 @@
         goto Exit;
     }
 
+    if ( format_tag != 0x10000UL && format_tag != 0x74727565UL )
+      goto Bad_Format;
+
     /* the format tag was read, now check the rest of the header */
     sfnt->format_tag = format_tag;
     sfnt->offset     = offset;
@@ -351,6 +354,7 @@
     error = sfnt_dir_check( stream, offset, sfnt->num_tables );
     if ( error )
     {
+    Bad_Format:
       FT_TRACE2(( "TT_Load_SFNT_Header: file is not SFNT!\n" ));
       error = SFNT_Err_Unknown_File_Format;
     }