diff --git a/src/Utils/Lookup.php b/src/Utils/Lookup.php
index 37f74b5..c633c4d 100644
--- a/src/Utils/Lookup.php
+++ b/src/Utils/Lookup.php
@@ -110,6 +110,11 @@ public static function resourceOpcode(
             $opcode = $opcode->getValue();
         }
         if (is_string($opcode)) {
+            if ($opcode === '') {
+                throw new EmptyArgumentException(
+                    'OPCODE could not be empty string or whitespace only'
+                );
+            }
             $opcode = strtoupper(trim($opcode));
             $code = self::OPCODE_LIST[$opcode]??null;
             if (!$opcode) {