diff --git a/src/ftxgdef.c b/src/ftxgdef.c
index 449b2e2..60ad581 100644
--- a/src/ftxgdef.c
+++ b/src/ftxgdef.c
@@ -179,7 +179,7 @@
     if ( !retptr )
       return TT_Err_Invalid_Argument;
 
-    if (( error = tt_face->goto_table( tt_face, TTAG_GDEF, stream, 0 ) ))
+    if (( error = tt_face->goto_table( tt_face, TTAG_GDEF, stream, NULL ) ))
       return error;
 
     if (( error = TT_New_GDEF_Table ( face, &gdef ) ))
diff --git a/src/ftxgpos.c b/src/ftxgpos.c
index 962b666..3ac1348 100644
--- a/src/ftxgpos.c
+++ b/src/ftxgpos.c
@@ -102,7 +102,7 @@
     if ( !stream )
       return TT_Err_Invalid_Face_Handle;
 
-    if (( error = tt_face->goto_table( tt_face, TTAG_GPOS, stream, 0 ) ))
+    if (( error = tt_face->goto_table( tt_face, TTAG_GPOS, stream, NULL ) ))
       return error;
 
     base_offset = FILE_Pos();
@@ -663,7 +663,7 @@
       {
         an->af.af3.XDeviceTable.StartSize  = 0;
         an->af.af3.XDeviceTable.EndSize    = 0;
-        an->af.af3.XDeviceTable.DeltaValue = 0;
+        an->af.af3.XDeviceTable.DeltaValue = NULL;
       }
 
       if ( ACCESS_Frame( 2L ) )
@@ -688,7 +688,7 @@
       {
         an->af.af3.YDeviceTable.StartSize  = 0;
         an->af.af3.YDeviceTable.EndSize    = 0;
-        an->af.af3.YDeviceTable.DeltaValue = 0;
+        an->af.af3.YDeviceTable.DeltaValue = NULL;
       }
       break;
 
diff --git a/src/ftxgsub.c b/src/ftxgsub.c
index a5fb602..b7e4c13 100644
--- a/src/ftxgsub.c
+++ b/src/ftxgsub.c
@@ -90,7 +90,7 @@
     if ( !retptr )
       return TT_Err_Invalid_Argument;
 
-    if (( error = tt_face->goto_table( tt_face, TTAG_GSUB, stream, 0 ) ))
+    if (( error = tt_face->goto_table( tt_face, TTAG_GSUB, stream, NULL ) ))
       return error;
 
     base_offset = FILE_Pos();