diff --git a/src/tools/jwt.ts b/src/tools/jwt.ts
index 7d29b88..16c6db8 100644
--- a/src/tools/jwt.ts
+++ b/src/tools/jwt.ts
@@ -37,7 +37,7 @@ export function getEnvString(
 				keyName += `_${key[i].toLowerCase()}`;
 			}
 		}
-		keyName.toUpperCase();
+		keyName = keyName.toUpperCase();
 	} else {
 		// Non-global keys are parsed as passed
 		keyName = key;