diff --git a/C/stdpreds.c b/C/stdpreds.c
index be61a07b7..167fc6e70 100644
--- a/C/stdpreds.c
+++ b/C/stdpreds.c
@@ -2960,6 +2960,22 @@ Yap_IsOp(Atom at)
   return (!EndOfPAEntr(op));
 }
 
+int
+Yap_IsOpMaxPrio(Atom at)
+{
+  OpEntry *op = NextOp(RepOpProp((Prop)(RepAtom(at)->PropsOfAE)));
+  int max;
+
+  if (EndOfPAEntr(op))
+    return 0;
+  max = (op->Prefix & 0xfff);
+  if ((op->Infix & 0xfff) > max)
+    max = op->Infix & 0xfff;
+  if ((op->Posfix & 0xfff) > max)
+    max = op->Posfix & 0xfff;
+  return max;
+}
+
 static Int
 unify_op(OpEntry         *op)
 {
diff --git a/C/write.c b/C/write.c
index b1c122867..adffe0da6 100644
--- a/C/write.c
+++ b/C/write.c
@@ -214,12 +214,12 @@ legalAtom(unsigned char *s)			/* Is this a legal atom ? */
 
 static int LeftOpToProtect(Atom at, int p)
 {
-  return Yap_IsOp(at);
+  return Yap_IsOpMaxPrio(at) > p;
 }
 
 static int RightOpToProtect(Atom at, int p)
 {
-  return Yap_IsOp(at);
+  return Yap_IsOpMaxPrio(at) > p;
 }
 
 static wtype 
diff --git a/H/Yapproto.h b/H/Yapproto.h
index c22e385f3..65826d352 100644
--- a/H/Yapproto.h
+++ b/H/Yapproto.h
@@ -316,6 +316,7 @@ void	STD_PROTO(Yap_InitCPreds,(void));
 void	STD_PROTO(Yap_show_statistics,(void));
 void	STD_PROTO(Yap_signal,(yap_signals));
 void	STD_PROTO(Yap_undo_signal,(yap_signals));
+int	STD_PROTO(Yap_IsOpMaxPrio,(Atom));
 
 /* sysbits.c */
 void	STD_PROTO(Yap_set_fpu_exceptions,(int));