diff --git a/Userland/Libraries/LibWeb/CSS/ComputedValues.h b/Userland/Libraries/LibWeb/CSS/ComputedValues.h
index d9537e79cd..44ced91eb9 100644
--- a/Userland/Libraries/LibWeb/CSS/ComputedValues.h
+++ b/Userland/Libraries/LibWeb/CSS/ComputedValues.h
@@ -51,6 +51,8 @@ struct Transformation {
 struct FlexBasisData {
     CSS::FlexBasis type { CSS::FlexBasis::Auto };
     CSS::Length length {};
+
+    bool is_definite() const { return type == CSS::FlexBasis::Length; }
 };
 
 struct BoxShadowData {