Index: unique.c
===================================================================
--- unique.c	(revision 48503)
+++ unique.c	(working copy)
@@ -462,16 +462,18 @@
     for (i = 0; i < data.M; i++) h[i] = NIL;
     if(from_last)
 	for (i = n-1; i >= 0; i--) {
-#define IS_DUPLICATED_CHECK
-	    if(isDuplicated(x, i, &data)) {
-		Rboolean isDup = TRUE;
-		for(j = 0; j < m; j++)
-		    if(data.equal(x, i, incomp, j)) {
-			isDup = FALSE; break;
-		    }
-		if(isDup)
-		    return ++i;
-		/* else continue */
+#define IS_DUPLICATED_CHECK \
+	    if(isDuplicated(x, i, &data)) { \
+		Rboolean isDup = TRUE; \
+		for(j = 0; j < m; j++) \
+		    if(data.equal(x, i, incomp, j)) { \
+			isDup = FALSE; break; \
+		    } \
+		if(isDup) { \
+		    UNPROTECT(1); \
+		    return ++i; \
+                } \
+		/* else continue */ \
 	    }
 	    IS_DUPLICATED_CHECK;
 	}
@@ -480,6 +482,7 @@
             IS_DUPLICATED_CHECK;
     }
 
+    UNPROTECT(1) ;
     return 0;
 }