diff --git a/.cargo/config b/.cargo/config
index 2b26448..3b89a87 100644
--- a/.cargo/config
+++ b/.cargo/config
@@ -3,6 +3,7 @@ rustflags = [
   "-C", "link-arg=-Tlink.x",
   "-C", "target-feature=a9,armv7-a,neon",
   "-C", "target-cpu=cortex-a9",
+  "-Zcrate-attr=feature(const_fn)"
 ]
 
 [build]