diff --git a/rtree-c/src/ReduceC.hs b/rtree-c/src/ReduceC.hs
index 42cf7a96e00234696fb3f270af80a51877ae9927..576a047e8e69ff082766e71b796736a574d1694e 100644
--- a/rtree-c/src/ReduceC.hs
+++ b/rtree-c/src/ReduceC.hs
@@ -97,7 +97,7 @@ reduceCTranslUnit (C.CTranslUnit es ni) ctx = do
         if funIsStatic fun
           then do
             let fstr = C.identToString (funName fun)
-            isStatic <- check ("remove static from " <> fstr, funPosition fun)
+            isStatic <- not <$> check ("remove static from " <> fstr, funPosition fun)
             pure fun{funIsStatic = isStatic}
           else pure fun
       else pure _functions