diff --git a/config.nims b/config.nims
index a7ff6468c..a69cddc09 100644
--- a/config.nims
+++ b/config.nims
@@ -3,7 +3,7 @@
 if defined(arm64):
   # https://twitter.com/EthereumOnARM/status/1309477357938499585?s=20
   # https://github.com/supranational/blst/issues/31
-  switch("defined", "BLS_FORCE_BACKEND=miracl")
+  switch("define", "BLS_FORCE_BACKEND=miracl")
 
 # ---------------------------------------------------