diff --git a/packages/core/pattern.mjs b/packages/core/pattern.mjs
index 84441a1b..48e52643 100644
--- a/packages/core/pattern.mjs
+++ b/packages/core/pattern.mjs
@@ -1294,8 +1294,8 @@ export function slowcatPrime(...pats) {
   pats = pats.map(reify);
   const query = function (state) {
     const pat_n = Math.floor(state.span.begin) % pats.length;
-    const pat = pats[pat_n];
-    return pat.query(state);
+    const pat = pats[pat_n]; // can be undefined for same cases e.g. /#cHVyZSg0MikKICAuZXZlcnkoMyxhZGQoNykpCiAgLmxhdGUoLjUp
+    return pat?.query(state) || [];
   };
   return new Pattern(query)._splitQueries();
 }