diff --git a/packages/core/pattern.mjs b/packages/core/pattern.mjs
index 84441a1b7..48e52643a 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();
 }
diff --git a/packages/core/util.mjs b/packages/core/util.mjs
index 6a96be877..86d798d6c 100644
--- a/packages/core/util.mjs
+++ b/packages/core/util.mjs
@@ -53,8 +53,8 @@ export const getPlayableNoteValue = (hap) => {
   // if value is number => interpret as midi number as long as its not marked as frequency
   if (typeof note === 'number' && context.type !== 'frequency') {
     note = fromMidi(hap.value);
-  } else if (typeof note === 'string' && !isNote(note)) {
-    throw new Error('not a note: ' + note);
+  } else if (typeof note !== 'string' || !isNote(note)) {
+    throw new Error('not a note: ' + JSON.stringify(note));
   }
   return note;
 };