diff --git a/deflate.c b/deflate.c
index 801c407035543e1152eba63c4e689afe791cb5a2..537c4a3dbfb94ab152fda84f5f03f837e4b3f2fe 100644
--- a/deflate.c
+++ b/deflate.c
@@ -73,6 +73,7 @@ typedef enum {
 typedef block_state (*compress_func) OF((deflate_state *s, int flush));
 /* Compression function. Returns the block state after the call. */
 
+local int deflateStateCheck      OF((z_streamp strm));
 local void fill_window    OF((deflate_state *s));
 local block_state deflate_stored OF((deflate_state *s, int flush));
 local block_state deflate_fast   OF((deflate_state *s, int flush));
@@ -271,6 +272,7 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
     if (s == Z_NULL) return Z_MEM_ERROR;
     strm->state = (struct internal_state FAR *)s;
     s->strm = strm;
+    s->status = INIT_STATE;     /* to pass state test in deflateReset() */
 
     s->wrap = wrap;
     s->gzhead = Z_NULL;
@@ -312,6 +314,28 @@ int ZEXPORT deflateInit2_(strm, level, method, windowBits, memLevel, strategy,
     return deflateReset(strm);
 }
 
+/* =========================================================================
+ * Check for a valid deflate stream state. Return 0 if ok, 1 if not.
+ */
+local int deflateStateCheck (strm)
+    z_streamp strm;
+{
+    deflate_state *s;
+    if (strm == Z_NULL ||
+        strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0)
+        return 1;
+    s = strm->state;
+    if (s == Z_NULL || s->strm != strm || (s->status != INIT_STATE &&
+                                           s->status != EXTRA_STATE &&
+                                           s->status != NAME_STATE &&
+                                           s->status != COMMENT_STATE &&
+                                           s->status != HCRC_STATE &&
+                                           s->status != BUSY_STATE &&
+                                           s->status != FINISH_STATE))
+        return 1;
+    return 0;
+}
+
 /* ========================================================================= */
 int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
     z_streamp strm;
@@ -324,7 +348,7 @@ int ZEXPORT deflateSetDictionary (strm, dictionary, dictLength)
     unsigned avail;
     z_const unsigned char *next;
 
-    if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL)
+    if (deflateStateCheck(strm) || dictionary == Z_NULL)
         return Z_STREAM_ERROR;
     s = strm->state;
     wrap = s->wrap;
@@ -387,8 +411,7 @@ int ZEXPORT deflateResetKeep (strm)
 {
     deflate_state *s;
 
-    if (strm == Z_NULL || strm->state == Z_NULL ||
-        strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0) {
+    if (deflateStateCheck(strm)) {
         return Z_STREAM_ERROR;
     }
 
@@ -433,8 +456,8 @@ int ZEXPORT deflateSetHeader (strm, head)
     z_streamp strm;
     gz_headerp head;
 {
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
-    if (strm->state->wrap != 2) return Z_STREAM_ERROR;
+    if (deflateStateCheck(strm) || strm->state->wrap != 2)
+        return Z_STREAM_ERROR;
     strm->state->gzhead = head;
     return Z_OK;
 }
@@ -445,7 +468,7 @@ int ZEXPORT deflatePending (strm, pending, bits)
     int *bits;
     z_streamp strm;
 {
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     if (pending != Z_NULL)
         *pending = strm->state->pending;
     if (bits != Z_NULL)
@@ -462,7 +485,7 @@ int ZEXPORT deflatePrime (strm, bits, value)
     deflate_state *s;
     int put;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
     if ((Bytef *)(s->d_buf) < s->pending_out + ((Buf_size + 7) >> 3))
         return Z_BUF_ERROR;
@@ -489,7 +512,7 @@ int ZEXPORT deflateParams(strm, level, strategy)
     compress_func func;
     int err = Z_OK;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
 
 #ifdef FASTEST
@@ -529,7 +552,7 @@ int ZEXPORT deflateTune(strm, good_length, max_lazy, nice_length, max_chain)
 {
     deflate_state *s;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
     s->good_match = (uInt)good_length;
     s->max_lazy_match = (uInt)max_lazy;
@@ -568,7 +591,7 @@ uLong ZEXPORT deflateBound(strm, sourceLen)
               ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
 
     /* if can't get parameters, return conservative bound plus zlib wrapper */
-    if (strm == Z_NULL || strm->state == Z_NULL)
+    if (deflateStateCheck(strm))
         return complen + 6;
 
     /* compute wrapper length */
@@ -661,8 +684,7 @@ int ZEXPORT deflate (strm, flush)
     int old_flush; /* value of flush param for previous deflate call */
     deflate_state *s;
 
-    if (strm == Z_NULL || strm->state == Z_NULL ||
-        flush > Z_BLOCK || flush < 0) {
+    if (deflateStateCheck(strm) || flush > Z_BLOCK || flush < 0) {
         return Z_STREAM_ERROR;
     }
     s = strm->state;
@@ -973,18 +995,9 @@ int ZEXPORT deflateEnd (strm)
 {
     int status;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
 
     status = strm->state->status;
-    if (status != INIT_STATE &&
-        status != EXTRA_STATE &&
-        status != NAME_STATE &&
-        status != COMMENT_STATE &&
-        status != HCRC_STATE &&
-        status != BUSY_STATE &&
-        status != FINISH_STATE) {
-      return Z_STREAM_ERROR;
-    }
 
     /* Deallocate in reverse order of allocations: */
     TRY_FREE(strm, strm->state->pending_buf);
@@ -1015,7 +1028,7 @@ int ZEXPORT deflateCopy (dest, source)
     ushf *overlay;
 
 
-    if (source == Z_NULL || dest == Z_NULL || source->state == Z_NULL) {
+    if (deflateStateCheck(source) || dest == Z_NULL) {
         return Z_STREAM_ERROR;
     }
 
diff --git a/inflate.c b/inflate.c
index eb1b4ce6a7a07c972ebd2869cf0ff07bccb8afbd..0372edfda762908c9a45335cd6ff734b89e90b21 100644
--- a/inflate.c
+++ b/inflate.c
@@ -92,6 +92,7 @@
 #endif
 
 /* function prototypes */
+local int inflateStateCheck OF((z_streamp strm));
 local void fixedtables OF((struct inflate_state FAR *state));
 local int updatewindow OF((z_streamp strm, const unsigned char FAR *end,
                            unsigned copy));
@@ -101,12 +102,26 @@ local int updatewindow OF((z_streamp strm, const unsigned char FAR *end,
 local unsigned syncsearch OF((unsigned FAR *have, const unsigned char FAR *buf,
                               unsigned len));
 
+local int inflateStateCheck(strm)
+z_streamp strm;
+{
+    struct inflate_state FAR *state;
+    if (strm == Z_NULL ||
+        strm->zalloc == (alloc_func)0 || strm->zfree == (free_func)0)
+        return 1;
+    state = (struct inflate_state FAR *)strm->state;
+    if (state == Z_NULL || state->strm != strm ||
+        state->mode < HEAD || state->mode > SYNC)
+        return 1;
+    return 0;
+}
+
 int ZEXPORT inflateResetKeep(strm)
 z_streamp strm;
 {
     struct inflate_state FAR *state;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     strm->total_in = strm->total_out = state->total = 0;
     strm->msg = Z_NULL;
@@ -131,7 +146,7 @@ z_streamp strm;
 {
     struct inflate_state FAR *state;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     state->wsize = 0;
     state->whave = 0;
@@ -147,7 +162,7 @@ int windowBits;
     struct inflate_state FAR *state;
 
     /* get the state */
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
 
     /* extract wrap request from windowBits parameter */
@@ -210,7 +225,9 @@ int stream_size;
     if (state == Z_NULL) return Z_MEM_ERROR;
     Tracev((stderr, "inflate: allocated\n"));
     strm->state = (struct internal_state FAR *)state;
+    state->strm = strm;
     state->window = Z_NULL;
+    state->mode = HEAD;     /* to pass state test in inflateReset2() */
     ret = inflateReset2(strm, windowBits);
     if (ret != Z_OK) {
         ZFREE(strm, state);
@@ -234,7 +251,7 @@ int value;
 {
     struct inflate_state FAR *state;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     if (bits < 0) {
         state->hold = 0;
@@ -625,7 +642,7 @@ int flush;
     static const unsigned short order[19] = /* permutation of code lengths */
         {16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15};
 
-    if (strm == Z_NULL || strm->state == Z_NULL || strm->next_out == Z_NULL ||
+    if (inflateStateCheck(strm) || strm->next_out == Z_NULL ||
         (strm->next_in == Z_NULL && strm->avail_in != 0))
         return Z_STREAM_ERROR;
 
@@ -1261,7 +1278,7 @@ int ZEXPORT inflateEnd(strm)
 z_streamp strm;
 {
     struct inflate_state FAR *state;
-    if (strm == Z_NULL || strm->state == Z_NULL || strm->zfree == (free_func)0)
+    if (inflateStateCheck(strm))
         return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     if (state->window != Z_NULL) ZFREE(strm, state->window);
@@ -1279,7 +1296,7 @@ uInt *dictLength;
     struct inflate_state FAR *state;
 
     /* check state */
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
 
     /* copy dictionary */
@@ -1304,7 +1321,7 @@ uInt dictLength;
     int ret;
 
     /* check state */
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     if (state->wrap != 0 && state->mode != DICT)
         return Z_STREAM_ERROR;
@@ -1336,7 +1353,7 @@ gz_headerp head;
     struct inflate_state FAR *state;
 
     /* check state */
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     if ((state->wrap & 2) == 0) return Z_STREAM_ERROR;
 
@@ -1389,7 +1406,7 @@ z_streamp strm;
     struct inflate_state FAR *state;
 
     /* check parameters */
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     if (strm->avail_in == 0 && state->bits < 8) return Z_BUF_ERROR;
 
@@ -1436,7 +1453,7 @@ z_streamp strm;
 {
     struct inflate_state FAR *state;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     return state->mode == STORED && state->bits == 0;
 }
@@ -1451,8 +1468,7 @@ z_streamp source;
     unsigned wsize;
 
     /* check input */
-    if (dest == Z_NULL || source == Z_NULL || source->state == Z_NULL ||
-        source->zalloc == (alloc_func)0 || source->zfree == (free_func)0)
+    if (inflateStateCheck(source) || dest == Z_NULL)
         return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)source->state;
 
@@ -1473,6 +1489,7 @@ z_streamp source;
     /* copy state */
     zmemcpy((voidpf)dest, (voidpf)source, sizeof(z_stream));
     zmemcpy((voidpf)copy, (voidpf)state, sizeof(struct inflate_state));
+    copy->strm = dest;
     if (state->lencode >= state->codes &&
         state->lencode <= state->codes + ENOUGH - 1) {
         copy->lencode = copy->codes + (state->lencode - state->codes);
@@ -1494,7 +1511,7 @@ int subvert;
 {
     struct inflate_state FAR *state;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
 #ifdef INFLATE_ALLOW_INVALID_DISTANCE_TOOFAR_ARRR
     state->sane = !subvert;
@@ -1512,7 +1529,7 @@ int check;
 {
     struct inflate_state FAR *state;
 
-    if (strm == Z_NULL || strm->state == Z_NULL) return Z_STREAM_ERROR;
+    if (inflateStateCheck(strm)) return Z_STREAM_ERROR;
     state = (struct inflate_state FAR *)strm->state;
     if (check)
         state->wrap |= 4;
@@ -1526,7 +1543,7 @@ z_streamp strm;
 {
     struct inflate_state FAR *state;
 
-    if (strm == Z_NULL || strm->state == Z_NULL)
+    if (inflateStateCheck(strm))
         return -(1L << 16);
     state = (struct inflate_state FAR *)strm->state;
     return (long)(((unsigned long)((long)state->back)) << 16) +
@@ -1538,7 +1555,7 @@ unsigned long ZEXPORT inflateCodesUsed(strm)
 z_streamp strm;
 {
     struct inflate_state FAR *state;
-    if (strm == Z_NULL || strm->state == Z_NULL) return (unsigned long)0 - 1;
+    if (inflateStateCheck(strm)) return (unsigned long)0 - 1;
     state = (struct inflate_state FAR *)strm->state;
     return (unsigned long)(state->next - state->codes);
 }
diff --git a/inflate.h b/inflate.h
index ed434e5e88da5ce6b106ea0218ce763ddd0469bb..047124d30ca4a94aea54e3d5606a9e164cc5dd74 100644
--- a/inflate.h
+++ b/inflate.h
@@ -18,7 +18,7 @@
 
 /* Possible inflate modes between inflate() calls */
 typedef enum {
-    HEAD,       /* i: waiting for magic header */
+    HEAD = 16180,   /* i: waiting for magic header */
     FLAGS,      /* i: waiting for method and flags (gzip) */
     TIME,       /* i: waiting for modification time (gzip) */
     OS,         /* i: waiting for extra flags and operating system (gzip) */
@@ -80,6 +80,7 @@ typedef enum {
 /* State maintained between inflate() calls -- approximately 7K bytes, not
    including the allocated sliding window, which is up to 32K bytes. */
 struct inflate_state {
+    z_streamp strm;             /* pointer back to this zlib stream */
     inflate_mode mode;          /* current inflate mode */
     int last;                   /* true if processing last block */
     int wrap;                   /* bit 0 true for zlib, bit 1 true for gzip,