diff --git a/yoga/numeric/FloatOptional.h b/yoga/numeric/FloatOptional.h
index bc5790d4..d1e2bc7e 100644
--- a/yoga/numeric/FloatOptional.h
+++ b/yoga/numeric/FloatOptional.h
@@ -30,7 +30,7 @@ struct FloatOptional {
   }
 
   constexpr bool isUndefined() const {
-    return yoga::isUndefined(value);
+    return yoga::isUndefined(value_);
   }
 };