diff --git a/include/osg/Texture b/include/osg/Texture
index eec1e98ea..6530fdce3 100644
--- a/include/osg/Texture
+++ b/include/osg/Texture
@@ -76,6 +76,7 @@
 #endif
 
 #ifndef GL_TEXTURE_COMPARE_MODE_ARB
+#define GL_DEPTH_TEXTURE_MODE_ARB         0x884B
 #define GL_TEXTURE_COMPARE_MODE_ARB       0x884C
 #define GL_TEXTURE_COMPARE_FUNC_ARB       0x884D
 #define GL_COMPARE_R_TO_TEXTURE_ARB       0x884E