diff --git a/src/gzip/ftgzip.c b/src/gzip/ftgzip.c
index 9fabb6934..8de1d4b38 100644
--- a/src/gzip/ftgzip.c
+++ b/src/gzip/ftgzip.c
@@ -55,7 +55,7 @@
   /* original ZLib.                                                 */
 
 #ifndef USE_ZLIB_ZCALLOC
-/* #define MY_ZCALLOC */ /* prevent all zcalloc() & zfree() in zutil.c */
+ #define MY_ZCALLOC /* prevent all zcalloc() & zfree() in zutil.c */
 #endif
 
   /* Note that our `zlib.h' includes `ftzconf.h' instead of `zconf.h'; */
@@ -165,7 +165,6 @@
 
 #if !defined( FT_CONFIG_OPTION_SYSTEM_ZLIB ) && !defined( USE_ZLIB_ZCALLOC )
 
-/*
   local voidpf
   zcalloc ( voidpf    opaque,
             unsigned  items,
@@ -181,7 +180,6 @@
     ft_gzip_free( (FT_Memory)opaque, ptr );
   }
 
-*/
 #endif /* !SYSTEM_ZLIB && !USE_ZLIB_ZCALLOC */
 
 
diff --git a/src/gzip/zconf.h b/src/gzip/ftzconf.h
similarity index 100%
rename from src/gzip/zconf.h
rename to src/gzip/ftzconf.h
diff --git a/src/gzip/rules.mk b/src/gzip/rules.mk
index e10217a02..512d51ea6 100644
--- a/src/gzip/rules.mk
+++ b/src/gzip/rules.mk
@@ -43,7 +43,7 @@ GZIP_DRV_SRCS := $(GZIP_DIR)/inftrees.c  \
                  $(GZIP_DIR)/gzread.c    \
                  $(GZIP_DIR)/inftrees.h  \
                  $(GZIP_DIR)/deflate.c   \
-                 $(GZIP_DIR)/zconf.h     \
+                 $(GZIP_DIR)/ftzconf.h   \
                  $(GZIP_DIR)/trees.c     \
                  $(GZIP_DIR)/inffast.c   \
                  $(GZIP_DIR)/inflate.c   \
diff --git a/src/gzip/zlib.h b/src/gzip/zlib.h
index f09cdaf1e..e91a3ca3d 100644
--- a/src/gzip/zlib.h
+++ b/src/gzip/zlib.h
@@ -31,7 +31,7 @@
 #ifndef ZLIB_H
 #define ZLIB_H
 
-#include "zconf.h"
+#include "ftzconf.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/src/gzip/zutil.h b/src/gzip/zutil.h
index b079ea6a8..f35b7cafb 100644
--- a/src/gzip/zutil.h
+++ b/src/gzip/zutil.h
@@ -106,7 +106,7 @@ extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
 #if defined(VAXC) || defined(VMS)
 #  define OS_CODE  2
 #  define F_OPEN(name, mode) \
-     fopen((name), (mode), "mbc=60", "ctx=stm", "rfm=fix", "mrs=512")
+     ft_fopen((name), (mode), "mbc=60", "ctx=stm", "rfm=fix", "mrs=512")
 #endif
 
 #ifdef __370__
@@ -223,9 +223,9 @@ extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
 #    define zmemcmp _fmemcmp
 #    define zmemzero(dest, len) _fmemset(dest, 0, len)
 #  else
-#    define zmemcpy memcpy
-#    define zmemcmp memcmp
-#    define zmemzero(dest, len) memset(dest, 0, len)
+#    define zmemcpy ft_memcpy
+#    define zmemcmp ft_memcmp
+#    define zmemzero(dest, len) ft_memset(dest, 0, len)
 #  endif
 #else
    void ZLIB_INTERNAL zmemcpy OF((Bytef* dest, const Bytef* source, uInt len));
@@ -254,9 +254,9 @@ extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
 #endif
 
 #ifndef Z_SOLO
-   voidpf ZLIB_INTERNAL zcalloc OF((voidpf opaque, unsigned items,
+   static voidpf zcalloc OF((voidpf opaque, unsigned items,
                                     unsigned size));
-   void ZLIB_INTERNAL zcfree  OF((voidpf opaque, voidpf ptr));
+   static void zcfree  OF((voidpf opaque, voidpf ptr));
 #endif
 
 #define ZALLOC(strm, items, size) \