diff --git a/mozilla/nsprpub/pr/src/io/prscanf.c b/mozilla/nsprpub/pr/src/io/prscanf.c
index 8a29af356b7..66bdd0d757f 100644
--- a/mozilla/nsprpub/pr/src/io/prscanf.c
+++ b/mozilla/nsprpub/pr/src/io/prscanf.c
@@ -184,7 +184,12 @@ _pr_strtoull(const char *str, char **endptr, int base)
     }
 
     if (negative) {
+#ifdef HAVE_LONG_LONG
+        /* The cast to a signed type is to avoid a compiler warning */
+        x = -(PRInt64)x;
+#else
         LL_NEG(x, x);
+#endif
     }
 
     if (endptr) {