diff --git a/external/zlib/gzlib.c b/external/zlib/gzlib.c
index 983153c..bd243cc 100644
--- a/external/zlib/gzlib.c
+++ b/external/zlib/gzlib.c
@@ -4,6 +4,8 @@
  */
 
 #include "gzguts.h"
+#include <sys/types.h>
+#include <unistd.h>
 
 #if defined(_WIN32) && !defined(__BORLANDC__)
 #  define LSEEK _lseeki64
diff --git a/external/zlib/gzread.c b/external/zlib/gzread.c
index 4168cbc..5c0d651 100644
--- a/external/zlib/gzread.c
+++ b/external/zlib/gzread.c
@@ -4,6 +4,7 @@
  */
 
 #include "gzguts.h"
+#include <unistd.h>
 
 /* Use read() to load a buffer -- return -1 on error, otherwise 0.  Read from
    state->fd, and update state->eof, state->err, and state->msg as appropriate.
diff --git a/external/zlib/gzwrite.c b/external/zlib/gzwrite.c
index 435b462..a6fcbdd 100644
--- a/external/zlib/gzwrite.c
+++ b/external/zlib/gzwrite.c
@@ -4,6 +4,7 @@
  */
 
 #include "gzguts.h"
+#include <unistd.h>
 
 /* Initialize state for writing a gzip file.  Mark initialization by setting
    state->size to non-zero.  Return -1 on a memory allocation failure, or 0 on