diff --git a/src/lib/components/transitions/TransitionChild.svelte b/src/lib/components/transitions/TransitionChild.svelte
index 184b07e..7cb8cc3 100644
--- a/src/lib/components/transitions/TransitionChild.svelte
+++ b/src/lib/components/transitions/TransitionChild.svelte
@@ -163,7 +163,7 @@
   // from blowing away the transition classes
   $: classes = isTransitioning
     ? container?.className
-    : `${$$props.class} ${entered}`;
+    : `${$$props.class || ""} ${entered}`;
 </script>
 
 <div bind:this={container} {...$$restProps} class={classes}>