--- libmng_zlib.c
+++ libmng_zlib.c
@@ -162,6 +162,10 @@
 #ifdef MNG_SUPPORT_TRACE
   MNG_TRACE (pData, MNG_FN_ZLIB_INFLATEINIT, MNG_LC_START);
 #endif
+
+  if (pData->bInflating)               /* free the old zlib structures */
+     inflateEnd(&pData->sZlib);
+
                                        /* initialize zlib structures and such */
   iZrslt = inflateInit (&pData->sZlib);