diff --git a/os/format.c b/os/format.c
index cdec7893f..8e5ccf014 100644
--- a/os/format.c
+++ b/os/format.c
@@ -1079,13 +1079,13 @@ static Int with_output_to(USES_REGS1) {
     return false;
   }
   if (IsApplTerm(tin) && (f = FunctorOfTerm(tin))) {
-      if(f == FunctorAtom || f == FunctorString || f == FunctorCodes1 ||
-       f == FunctorCodes || f == FunctorChars1 || f == FunctorChars)) {
-    output_stream = Yap_OpenBufWriteStream(PASS_REGS1);
-    my_mem_stream = true;
-    
-  } 
-  } else {
+	  if (f == FunctorAtom || f == FunctorString || f == FunctorCodes1 ||
+		  f == FunctorCodes || f == FunctorChars1 || f == FunctorChars) {
+		  output_stream = Yap_OpenBufWriteStream(PASS_REGS1);
+		  my_mem_stream = true;
+	  }
+  }
+  if (my_mem_stream){
     /* needs to change LOCAL_c_output_stream for write */
     output_stream = Yap_CheckStream(ARG1, Output_Stream_f, "format/3");
     my_mem_stream = false;
@@ -1121,15 +1121,17 @@ static Int format(Term tf, Term tas, Term tout USES_REGS) {
     return false;
   }
   yhandle_t hl = Yap_StartHandles(), yo = Yap_PushHandle(tout);
-  if (IsApplTerm(tout) && (f = FunctorOfTerm(tout)) &&
-      (f == FunctorAtom || f == FunctorString1 || f == FunctorCodes1 ||
-       f == FunctorCodes || f == FunctorChars1 || f == FunctorChars)) {
+  if (IsApplTerm(tout) && (f = FunctorOfTerm(tout))) {
+     if (f == FunctorAtom || f == FunctorString1 || f == FunctorCodes1 ||
+       f == FunctorCodes || f == FunctorChars1 || f == FunctorChars){
     output_stream = Yap_OpenBufWriteStream(PASS_REGS1);
     mem_stream = true;
-  } else {
+  }
+  if (!mem_stream) {
     /* needs to change LOCAL_c_output_stream for write */
     output_stream = Yap_CheckStream(tout, Output_Stream_f, "format/3");
   }
+  }
   if (output_stream == -1) {
     UNLOCK(GLOBAL_Stream[output_stream].streamlock);
     return false;