diff --git a/tools/tiffgt.c b/tools/tiffgt.c
index 245a2b45..5991d309 100644
--- a/tools/tiffgt.c
+++ b/tools/tiffgt.c
@@ -27,11 +27,16 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#if HAVE_UNISTD_H
 #include <unistd.h>
+#endif
 
 #ifdef HAVE_OPENGL_GL_H
 # include <OpenGL/gl.h>
 #else
+# ifdef _WIN32
+#  include <windows.h>
+# endif
 # include <GL/gl.h>
 #endif
 #ifdef HAVE_GLUT_GLUT_H