diff --git a/src/ExCSS/Parser/StylesheetComposer.cs b/src/ExCSS/Parser/StylesheetComposer.cs
index 8313da8..48c303d 100644
--- a/src/ExCSS/Parser/StylesheetComposer.cs
+++ b/src/ExCSS/Parser/StylesheetComposer.cs
@@ -657,6 +657,7 @@ public Property CreateDeclarationWith(Func<string, Property> createProperty, ref
 
                             property = new UnknownProperty(propertyName);
                             property.TrySetValue(value);
+                            property.IsImportant = important;
                             _nodes.Push(property);
                         }
                     }