1 files changed, 2 insertions, 0 deletions
diff --git a/progs/glsl/deriv.c b/progs/glsl/deriv.c
index e69f0b82c4..3fd674c331 100644
--- a/progs/glsl/deriv.c
+++ b/progs/glsl/deriv.c
@@ -13,6 +13,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <math.h>
+#include <GL/glew.h>
 #include <GL/gl.h>
 #include <GL/glut.h>
 #include <GL/glext.h>
@@ -228,6 +229,7 @@ main(int argc, char *argv[])
    glutInitWindowSize(200, 200);
    glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
    win = glutCreateWindow(argv[0]);
+   glewInit();
    glutReshapeFunc(Reshape);
    glutKeyboardFunc(Key);
    glutSpecialFunc(SpecialKey);