diff --git a/include/unzip.h b/include/unzip.h
index 3183968b7..493507e2b 100644
--- a/include/unzip.h
+++ b/include/unzip.h
@@ -47,13 +47,8 @@
 extern "C" {
 #endif
 
-#ifndef _ZLIB_H
 #include "zlib.h"
-#endif
-
-#ifndef  _ZLIBIOAPI_H
 #include "ioapi.h"
-#endif
 
 #ifdef HAVE_BZIP2
 #include "bzlib.h"
diff --git a/include/zip.h b/include/zip.h
index 6d045ca6f..ff0ae5674 100644
--- a/include/zip.h
+++ b/include/zip.h
@@ -47,10 +47,7 @@ extern "C" {
 //#define HAVE_BZIP2
 
 #include "zlib.h"
-
-#ifndef _ZLIBIOAPI_H
 #include "ioapi.h"
-#endif
 
 #ifdef HAVE_BZIP2
 #include "bzlib.h"
diff --git a/vs2015/zlib/contrib/minizip/unzip.h b/vs2015/zlib/contrib/minizip/unzip.h
index 2104e3915..9387ace5a 100644
--- a/vs2015/zlib/contrib/minizip/unzip.h
+++ b/vs2015/zlib/contrib/minizip/unzip.h
@@ -47,13 +47,8 @@
 extern "C" {
 #endif
 
-#ifndef _ZLIB_H
 #include "zlib.h"
-#endif
-
-#ifndef  _ZLIBIOAPI_H
 #include "ioapi.h"
-#endif
 
 #ifdef HAVE_BZIP2
 #include "bzlib.h"
diff --git a/vs2015/zlib/contrib/minizip/zip.h b/vs2015/zlib/contrib/minizip/zip.h
index 8aaebb623..ff0ae5674 100644
--- a/vs2015/zlib/contrib/minizip/zip.h
+++ b/vs2015/zlib/contrib/minizip/zip.h
@@ -46,13 +46,8 @@ extern "C" {
 
 //#define HAVE_BZIP2
 
-#ifndef _ZLIB_H
 #include "zlib.h"
-#endif
-
-#ifndef _ZLIBIOAPI_H
 #include "ioapi.h"
-#endif
 
 #ifdef HAVE_BZIP2
 #include "bzlib.h"