diff --git a/C/scanner.c b/C/scanner.c
index fa0594ca7..c8569772b 100755
--- a/C/scanner.c
+++ b/C/scanner.c
@@ -791,7 +791,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
   ScannerExtraBlocks = NULL;
   l = NULL;
   p = NULL;			/* Just to make lint happy */
-  LOCK(Stream[inp_stream].streamlock);
   ch = Nxtch(inp_stream);
   while (chtype(ch) == BS) {
     ch = Nxtch(inp_stream);
@@ -813,7 +812,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
       if (p)
 	p->Tok = Ord(kind = eot_tok);
       /* serious error now */
-      UNLOCK(Stream[inp_stream].streamlock);
       return l;
     }
     if (!l)
@@ -867,7 +865,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	  if (p)
 	    p->Tok = Ord(kind = eot_tok);
 	  /* serious error now */
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  return l;
 	}
 	add_ch_to_buff(ch);
@@ -894,7 +891,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	  if (p)
 	    t->Tok = Ord(kind = eot_tok);
 	  /* serious error now */
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  return l;
 	}
 	t->TokInfo = Unsigned(ae);
@@ -917,7 +913,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 
 	cherr = 0;
 	if (!(ptr = AllocScannerMemory(4096))) {
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  Yap_ErrorMessage = "Trail Overflow";
 	  Yap_Error_TYPE = OUT_OF_TRAIL_ERROR;	            
 	  if (p)
@@ -926,7 +921,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	  return l;
 	}
 	if (ASP-H < 1024) {
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  Yap_ErrorMessage = "Stack Overflow";
 	  Yap_Error_TYPE = OUT_OF_STACK_ERROR;	            
 	  Yap_Error_Size = 0L;	            
@@ -936,7 +930,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	  return l;
 	}
 	if ((t->TokInfo = get_num(&cha,&cherr,inp_stream,Nxtch,QuotedNxtch,ptr,4096,1)) == 0L) {
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  if (p)
 	    p->Tok = Ord(kind = eot_tok);
 	  /* serious error now */
@@ -950,7 +943,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	  t->TokPos = GetCurInpPos(inp_stream);
 	  e = (TokEntry *) AllocScannerMemory(sizeof(TokEntry));
 	  if (e == NULL) {
-	    UNLOCK(Stream[inp_stream].streamlock);
 	    Yap_ErrorMessage = "Trail Overflow";
 	    Yap_Error_TYPE = OUT_OF_TRAIL_ERROR;	            
 	    if (p)
@@ -980,7 +972,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	      t->TokPos = GetCurInpPos(inp_stream);
 	      e2 = (TokEntry *) AllocScannerMemory(sizeof(TokEntry));
 	      if (e2 == NULL) {
-		UNLOCK(Stream[inp_stream].streamlock);
 		Yap_ErrorMessage = "Trail Overflow";
 		Yap_Error_TYPE = OUT_OF_TRAIL_ERROR;	            
 		if (p)
@@ -1012,7 +1003,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	      t->TokPos = GetCurInpPos(inp_stream);
 	      e2 = (TokEntry *) AllocScannerMemory(sizeof(TokEntry));
 	      if (e2 == NULL) {
-		UNLOCK(Stream[inp_stream].streamlock);
 		Yap_ErrorMessage = "Trail Overflow";
 		Yap_Error_TYPE = OUT_OF_TRAIL_ERROR;	            
 		t->Tok = Ord(kind = eot_tok);
@@ -1078,7 +1068,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	}
 	++len;
 	if (charp > (char *)AuxSp - 1024) {
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  /* Not enough space to read in the string. */
 	  Yap_Error_TYPE = OUT_OF_AUXSPACE_ERROR;	  
 	  Yap_ErrorMessage = "not enough space to read in string or quoted atom";
@@ -1100,7 +1089,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	  mp = AllocScannerMemory(len + 1);
 	}
 	if (mp == NULL) {
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  Yap_ErrorMessage = "not enough heap space to read in string or quoted atom";
 	  Yap_ReleasePreAllocCodeSpace((CODEADDR)TokImage);
 	  t->Tok = Ord(kind = eot_tok);
@@ -1129,7 +1117,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	  if (p)
 	    t->Tok = Ord(kind = eot_tok);
 	  /* serious error now */
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  return l;
 	}
 	Yap_ReleasePreAllocCodeSpace((CODEADDR)TokImage);
@@ -1182,7 +1169,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
 	  if (p)
 	    t->Tok = Ord(kind = eot_tok);
 	  /* serious error now */
-	  UNLOCK(Stream[inp_stream].streamlock);
 	  return l;
 	}
 	Yap_ReleasePreAllocCodeSpace((CODEADDR)TokImage);
@@ -1253,7 +1239,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
       /* insert an error token to inform the system of what happened */
       TokEntry *e = (TokEntry *) AllocScannerMemory(sizeof(TokEntry));
       if (e == NULL) {
-	UNLOCK(Stream[inp_stream].streamlock);
 	Yap_ErrorMessage = "Trail Overflow";
 	Yap_Error_TYPE = OUT_OF_TRAIL_ERROR;	            
 	p->Tok = Ord(kind = eot_tok);
@@ -1269,7 +1254,6 @@ Yap_tokenizer(int inp_stream, Term *tposp)
       p = e;
     }
   } while (kind != eot_tok);
-  UNLOCK(Stream[inp_stream].streamlock);
   return (l);
 }