diff --git a/deps/rzlib/adler32.c b/deps/rzlib/adler32.c
index eeadf98d08..328449d5e1 100644
--- a/deps/rzlib/adler32.c
+++ b/deps/rzlib/adler32.c
@@ -156,12 +156,12 @@ local uLong adler32_combine_(uLong adler1, uLong adler2, z_off64_t len2)
 }
 
 /* ========================================================================= */
-uLong ZEXPORT adler32_combine(uLong adler1, uLong adler2, z_off_t len2)
+uLong adler32_combine(uLong adler1, uLong adler2, z_off_t len2)
 {
     return adler32_combine_(adler1, adler2, len2);
 }
 
-uLong ZEXPORT adler32_combine64(uLong adler1, uLong adler2, z_off64_t len2)
+uLong adler32_combine64(uLong adler1, uLong adler2, z_off64_t len2)
 {
     return adler32_combine_(adler1, adler2, len2);
 }
diff --git a/deps/rzlib/compress.c b/deps/rzlib/compress.c
index b161b05ddd..20e374b738 100644
--- a/deps/rzlib/compress.c
+++ b/deps/rzlib/compress.c
@@ -24,7 +24,7 @@ int ZEXPORT compress2 (Bytef *dest, uLongf *destLen, const Bytef *source, uLong
     z_stream stream;
     int err;
 
-    stream.next_in = (z_const Bytef *)source;
+    stream.next_in = (Bytef *)source;
     stream.avail_in = (uInt)sourceLen;
 #ifdef MAXSEG_64K
     /* Check for source > 64K on 16-bit machine: */
diff --git a/deps/rzlib/deflate.c b/deps/rzlib/deflate.c
index 15bfef9552..772d0b5aac 100644
--- a/deps/rzlib/deflate.c
+++ b/deps/rzlib/deflate.c
@@ -310,7 +310,7 @@ int ZEXPORT deflateSetDictionary (z_streamp strm, const Bytef *dictionary, uInt
     uInt str, n;
     int wrap;
     unsigned avail;
-    z_const unsigned char *next;
+    unsigned char *next;
 
     if (strm == Z_NULL || strm->state == Z_NULL || dictionary == Z_NULL)
         return Z_STREAM_ERROR;
@@ -340,7 +340,7 @@ int ZEXPORT deflateSetDictionary (z_streamp strm, const Bytef *dictionary, uInt
     avail = strm->avail_in;
     next = strm->next_in;
     strm->avail_in = dictLength;
-    strm->next_in = (z_const Bytef *)dictionary;
+    strm->next_in = (Bytef *)dictionary;
     fill_window(s);
     while (s->lookahead >= MIN_MATCH) {
         str = s->strstart;
diff --git a/deps/rzlib/gzwrite.c b/deps/rzlib/gzwrite.c
index 2f3d4260d8..9ee2af66e9 100644
--- a/deps/rzlib/gzwrite.c
+++ b/deps/rzlib/gzwrite.c
@@ -223,7 +223,7 @@ int ZEXPORT gzwrite(gzFile file, voidpc buf, unsigned len)
 
         /* directly compress user buffer to file */
         strm->avail_in = len;
-        strm->next_in = (z_const Bytef *)buf;
+        strm->next_in = (Bytef *)buf;
         state->x.pos += len;
         if (gz_comp(state, Z_NO_FLUSH) == -1)
             return 0;
diff --git a/deps/rzlib/inffast.c b/deps/rzlib/inffast.c
index 6c1e9de3b0..690b156c3c 100644
--- a/deps/rzlib/inffast.c
+++ b/deps/rzlib/inffast.c
@@ -67,8 +67,8 @@
 void ZLIB_INTERNAL inflate_fast(z_streamp strm, unsigned start)
 {
     struct inflate_state FAR *state;
-    z_const unsigned char FAR *in;      /* local strm->next_in */
-    z_const unsigned char FAR *last;    /* have enough input while in < last */
+    unsigned char FAR *in;      /* local strm->next_in */
+    unsigned char FAR *last;    /* have enough input while in < last */
     unsigned char FAR *out;     /* local strm->next_out */
     unsigned char FAR *beg;     /* inflate()'s initial strm->next_out */
     unsigned char FAR *end;     /* while out < end, enough space available */
diff --git a/deps/rzlib/inflate.c b/deps/rzlib/inflate.c
index a07345093d..b65283ac45 100644
--- a/deps/rzlib/inflate.c
+++ b/deps/rzlib/inflate.c
@@ -587,7 +587,7 @@ local int updatewindow(z_streamp strm, const Bytef *end, unsigned copy)
 int ZEXPORT inflate(z_streamp strm, int flush)
 {
     struct inflate_state FAR *state;
-    z_const unsigned char FAR *next;    /* next input */
+    unsigned char FAR *next;    /* next input */
     unsigned char FAR *put;     /* next output */
     unsigned have, left;        /* available input and output */
     unsigned long hold;         /* bit buffer */
diff --git a/deps/rzlib/uncompr.c b/deps/rzlib/uncompr.c
index 606cbe22fe..76a424aaea 100644
--- a/deps/rzlib/uncompr.c
+++ b/deps/rzlib/uncompr.c
@@ -26,7 +26,7 @@ int ZEXPORT uncompress (Bytef *dest, uLongf *destLen, const Bytef *source, uLong
     z_stream stream;
     int err;
 
-    stream.next_in = (z_const Bytef *)source;
+    stream.next_in = (Bytef *)source;
     stream.avail_in = (uInt)sourceLen;
     /* Check for source > 64K on 16-bit machine: */
     if ((uLong)stream.avail_in != sourceLen) return Z_BUF_ERROR;
diff --git a/deps/rzlib/unzip.c b/deps/rzlib/unzip.c
index 0689c99c18..0b94c13e6a 100644
--- a/deps/rzlib/unzip.c
+++ b/deps/rzlib/unzip.c
@@ -1696,7 +1696,7 @@ extern int ZEXPORT unzReadCurrentFile  (unzFile file, voidp buf, unsigned len)
         return UNZ_PARAMERROR;
 
 
-    if ((pfile_in_zip_read_info->read_buffer == NULL))
+    if (pfile_in_zip_read_info->read_buffer == NULL)
         return UNZ_END_OF_LIST_OF_FILE;
     if (len==0)
         return 0;
diff --git a/deps/rzlib/zutil.c b/deps/rzlib/zutil.c
index 41ad02ca29..822556f1c9 100644
--- a/deps/rzlib/zutil.c
+++ b/deps/rzlib/zutil.c
@@ -10,7 +10,7 @@
 #  include "gzguts.h"
 #endif
 
-z_const char * const z_errmsg[10] = {
+char * const z_errmsg[10] = {
 "need dictionary",     /* Z_NEED_DICT       2  */
 "stream end",          /* Z_STREAM_END      1  */
 "",                    /* Z_OK              0  */
diff --git a/deps/rzlib/zutil.h b/deps/rzlib/zutil.h
index 24ab06b1cf..5c6929f40b 100644
--- a/deps/rzlib/zutil.h
+++ b/deps/rzlib/zutil.h
@@ -44,7 +44,7 @@ typedef unsigned short ush;
 typedef ush FAR ushf;
 typedef unsigned long  ulg;
 
-extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
+extern char * const z_errmsg[10]; /* indexed by 2-zlib_error */
 /* (size given to avoid silly warnings with Visual C++) */
 
 #define ERR_MSG(err) z_errmsg[Z_NEED_DICT-(err)]