diff --git a/src/mesa/main/get.c b/src/mesa/main/get.c
index b943d69b71b..7570fab962c 100644
--- a/src/mesa/main/get.c
+++ b/src/mesa/main/get.c
@@ -172,6 +172,7 @@ union value {
    LOC_CONTEXT, type, offsetof(struct gl_context, field)
 #define ARRAY_FIELD(field, type) \
    LOC_ARRAY, type, offsetof(struct gl_array_object, field)
+#undef CONST /* already defined through windows.h */
 #define CONST(value) \
    LOC_CONTEXT, TYPE_CONST, value