diff --git a/src/crystal/spin_lock.cr b/src/crystal/spin_lock.cr
index 4255fcae7bbd..105c235e0c66 100644
--- a/src/crystal/spin_lock.cr
+++ b/src/crystal/spin_lock.cr
@@ -1,5 +1,5 @@
 # :nodoc:
-class Crystal::SpinLock
+struct Crystal::SpinLock
   private UNLOCKED = 0
   private LOCKED   = 1