diff --git a/C/pl-yap.c b/C/pl-yap.c
index 6fa9dabcc..16e0ba573 100755
--- a/C/pl-yap.c
+++ b/C/pl-yap.c
@@ -845,7 +845,7 @@ Yap_TermToString(Term t, char *s, size_t sz, size_t *length, int *encoding, int
   Int l;
 
   Yap_StartSlots( PASS_REGS1 );
-  l = Yap_InitSlot(t);
+  l = Yap_InitSlot(t  PASS_REGS );
 
   { IOENC encodings[3];
     IOENC *enc;