diff --git a/src/bnip/utils.py b/src/bnip/utils.py
index 489376d..9b7e653 100644
--- a/src/bnip/utils.py
+++ b/src/bnip/utils.py
@@ -14,4 +14,4 @@ def find_unique_or_set_base(unique_or_set_name) -> tuple[str, str]:
                 for set in sets:
                     if set.lower() == unique_or_set_name:
                         return key, "set"
-    return "",""
\ No newline at end of file
+    raise NipSyntaxError("NIP_0x23", f"'{unique_or_set_name}' is not a valid unique or set")