diff --git a/yoga/numeric/FloatOptional.h b/yoga/numeric/FloatOptional.h
index 62e22f36..99d43e93 100644
--- a/yoga/numeric/FloatOptional.h
+++ b/yoga/numeric/FloatOptional.h
@@ -29,7 +29,7 @@ struct FloatOptional {
     return isUndefined() ? defaultValue : value_;
   }
 
-  bool isUndefined() const {
+  constexpr bool isUndefined() const {
     return std::isnan(value_);
   }
 };