diff --git a/src/types/key/Key.ts b/src/types/key/Key.ts
index d470d1c2..f188d15b 100644
--- a/src/types/key/Key.ts
+++ b/src/types/key/Key.ts
@@ -561,7 +561,7 @@ export class Key {
     source: string,
     prefixes: Map<PrefixName, TypeID>
   ): PrefixName | undefined {
-    for (const [prefix, _] of prefixes) {
+    for (const [prefix] of prefixes) {
       if (source.startsWith(prefix)) {
         if (
           prefix === PrefixName.EraId &&