diff --git a/include/osg/Texture b/include/osg/Texture
index e753ebd92..79c40743c 100644
--- a/include/osg/Texture
+++ b/include/osg/Texture
@@ -36,12 +36,15 @@
 #define GL_COMPRESSED_RGB_ARB                   0x84ED
 #define GL_COMPRESSED_RGBA_ARB                  0x84EE
 #define GL_TEXTURE_COMPRESSION_HINT_ARB         0x84EF
-#define GL_TEXTURE_COMPRESSED_IMAGE_SIZE_ARB    0x86A0
 #define GL_TEXTURE_COMPRESSED_ARB               0x86A1
 #define GL_NUM_COMPRESSED_TEXTURE_FORMATS_ARB   0x86A2
 #define GL_COMPRESSED_TEXTURE_FORMATS_ARB       0x86A3
 #endif
 
+#ifndef GL_TEXTURE_COMPRESSED_IMAGE_SIZE_ARB
+#define GL_TEXTURE_COMPRESSED_IMAGE_SIZE_ARB    0x86A0
+#endif
+
 #ifndef GL_EXT_texture_compression_s3tc
 #define GL_COMPRESSED_RGB_S3TC_DXT1_EXT         0x83F0
 #define GL_COMPRESSED_RGBA_S3TC_DXT1_EXT        0x83F1