diff --git a/src/flam3.c b/src/flam3.c
index 9df618c..f15b335 100644
--- a/src/flam3.c
+++ b/src/flam3.c
@@ -28,13 +28,15 @@
 #include "parser.h"
 #include "filters.h"
 #include "palettes.h"
-#include "unistd.h"
 #include <limits.h>
 #include <locale.h>
 #include <math.h>
 #ifdef HAVE_STDINT_H
 #include <stdint.h>
 #endif
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
 #include <errno.h>
 
 #ifdef HAVE_LIBPTHREAD