diff --git a/lib/zlib/inffast.js b/lib/zlib/inffast.js
index 2fffbed..177aecf 100644
--- a/lib/zlib/inffast.js
+++ b/lib/zlib/inffast.js
@@ -180,6 +180,10 @@ module.exports = function inflate_fast(strm, start) {
                   state.mode = BAD;
                   break top;
                 }
+
+// (!) This block is disabled in zlib defailts,
+// don't enable it for binary compatibility
+
 //#ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
 //                if (len <= op - whave) {
 //                  do {
diff --git a/lib/zlib/trees.js b/lib/zlib/trees.js
index 7813d4e..3c56682 100644
--- a/lib/zlib/trees.js
+++ b/lib/zlib/trees.js
@@ -1139,7 +1139,7 @@ function _tr_tally(s, dist, lc)
 //    unsigned dist;  /* distance of matched string */
 //    unsigned lc;    /* match length-MIN_MATCH or unmatched char (if dist==0) */
 {
-  var out_length, in_length, dcode;
+  //var out_length, in_length, dcode;
 
   s.pending_buf[s.d_buf + s.last_lit * 2]     = (dist >>> 8) & 0xff;
   s.pending_buf[s.d_buf + s.last_lit * 2 + 1] = dist & 0xff;
@@ -1162,23 +1162,28 @@ function _tr_tally(s, dist, lc)
     s.dyn_dtree[d_code(dist) * 2]/*.Freq*/++;
   }
 
-  /* Try to guess if it is profitable to stop the current block here */
-  if ((s.last_lit & 0x1fff) === 0 && s.level > 2) {
-    /* Compute an upper bound for the compressed length */
-    out_length = s.last_lit*8;
-    in_length = s.strstart - s.block_start;
+// (!) This block is disabled in zlib defailts,
+// don't enable it for binary compatibility
 
-    for (dcode = 0; dcode < D_CODES; dcode++) {
-      out_length += s.dyn_dtree[dcode*2]/*.Freq*/ * (5 + extra_dbits[dcode]);
-    }
-    out_length >>>= 3;
-    //Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
-    //       s->last_lit, in_length, out_length,
-    //       100L - out_length*100L/in_length));
-    if (s.matches < (s.last_lit>>1)/*int /2*/ && out_length < (in_length>>1)/*int /2*/) {
-      return true;
-    }
-  }
+//#ifdef TRUNCATE_BLOCK
+//  /* Try to guess if it is profitable to stop the current block here */
+//  if ((s.last_lit & 0x1fff) === 0 && s.level > 2) {
+//    /* Compute an upper bound for the compressed length */
+//    out_length = s.last_lit*8;
+//    in_length = s.strstart - s.block_start;
+//
+//    for (dcode = 0; dcode < D_CODES; dcode++) {
+//      out_length += s.dyn_dtree[dcode*2]/*.Freq*/ * (5 + extra_dbits[dcode]);
+//    }
+//    out_length >>>= 3;
+//    //Tracev((stderr,"\nlast_lit %u, in %ld, out ~%ld(%ld%%) ",
+//    //       s->last_lit, in_length, out_length,
+//    //       100L - out_length*100L/in_length));
+//    if (s.matches < (s.last_lit>>1)/*int /2*/ && out_length < (in_length>>1)/*int /2*/) {
+//      return true;
+//    }
+//  }
+//#endif
 
   return (s.last_lit === s.lit_bufsize-1);
   /* We avoid equality with lit_bufsize because of wraparound at 64K