diff --git a/src/index.tsx b/src/index.tsx
index 0e260d4..acb1b8f 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -9,6 +9,9 @@ export function clearStyles() {
   for (const key in themes) delete themes[key]
 }
 
+// HMR support - clear styles when module is replaced
+import.meta.hot?.dispose(() => clearStyles())
+
 export function createTheme<const T extends Record<string, string | number>>(name: string, values: T): T {
   themes[name] = values as Record<string, string | number>
   return values
@@ -279,11 +282,7 @@ export function define(nameOrDef: string | TagDef, defIfNamed?: TagDef) {
   const def = defIfNamed ?? nameOrDef as TagDef
   const name = defIfNamed ? (nameOrDef as string) : anonName(def)
 
-  // Clear any existing styles for this component (supports HMR/hot reload)
-  for (const key in styles) {
-    if (key === name || key.startsWith(`${name}_`) || key.startsWith(`${name}.`) || key.startsWith(`${name}:`))
-      delete styles[key]
-  }
+  if (styles[name]) throw `${name} is already defined! Must use unique names.`
   registerStyles(name, def)
 
   return (props: Record<string, any>) => {