diff --git a/mozilla/modules/zlib/src/infblock.c b/mozilla/modules/zlib/src/infblock.c
index f4920faa5ea..b1fcbeea2f5 100644
--- a/mozilla/modules/zlib/src/infblock.c
+++ b/mozilla/modules/zlib/src/infblock.c
@@ -249,10 +249,12 @@ int r;
                              &s->sub.trees.tb, s->hufts, z);
       if (t != Z_OK)
       {
-        ZFREE(z, s->sub.trees.blens);
         r = t;
         if (r == Z_DATA_ERROR)
+        {
+          ZFREE(z, s->sub.trees.blens);
           s->mode = BAD;
+        }
         LEAVE
       }
       s->sub.trees.index = 0;
@@ -313,14 +315,17 @@ int r;
         t = inflate_trees_dynamic(257 + (t & 0x1f), 1 + ((t >> 5) & 0x1f),
                                   s->sub.trees.blens, &bl, &bd, &tl, &td,
                                   s->hufts, z);
-        ZFREE(z, s->sub.trees.blens);
         if (t != Z_OK)
         {
           if (t == (uInt)Z_DATA_ERROR)
+          {
+            ZFREE(z, s->sub.trees.blens);
             s->mode = BAD;
+          }
           r = t;
           LEAVE
         }
+        ZFREE(z, s->sub.trees.blens);
         Tracev((stderr, "inflate:       trees ok\n"));
         if ((c = inflate_codes_new(bl, bd, tl, td, z)) == Z_NULL)
         {