diff --git a/src/ftxgsub.c b/src/ftxgsub.c
index 6cdf3bd6f..6b9d4faf4 100644
--- a/src/ftxgsub.c
+++ b/src/ftxgsub.c
@@ -352,19 +352,6 @@
         if ( lo[i].LookupFlag & IGNORE_SPECIAL_MARKS )
         {
           if ( FILE_Seek( gdef->MarkAttachClassDef_offset ) ||
-               ACCESS_Frame( 2L ) )
-            goto Fail1;
-
-          new_offset = GET_UShort();
-
-          FORGET_Frame();
-
-          if ( !new_offset )
-            return TTO_Err_Invalid_GDEF_SubTable;
-
-          new_offset += base_offset;
-
-          if ( FILE_Seek( new_offset ) ||
                ( error = Load_ClassDefinition( &gdef->MarkAttachClassDef,
                                                256, stream ) ) != TT_Err_Ok )
             goto Fail1;
diff --git a/src/ftxopen.c b/src/ftxopen.c
index c721eec31..3101d6fd8 100644
--- a/src/ftxopen.c
+++ b/src/ftxopen.c
@@ -1459,7 +1459,7 @@
 
     f = d->DeltaFormat;
 
-    if ( size >= d->StartSize && size <= d->EndSize )
+    if ( d->DeltaValue && size >= d->StartSize && size <= d->EndSize )
     {
       s    = size - d->StartSize;
       byte = d->DeltaValue[s >> ( 4 - f )];