diff --git a/templates/team_setup.html b/templates/team_setup.html
index 6d6d2f3..fa386f2 100644
--- a/templates/team_setup.html
+++ b/templates/team_setup.html
@@ -260,18 +260,28 @@
         e.preventDefault();
         const key = e.key.toUpperCase();
         
+        // Entferne Event-Listener sofort
+        document.removeEventListener('keydown', handleKeyPress);
+        
         // Prüfe ob Taste bereits vergeben
-        const usedKeys = Object.values(keyMappings).filter((v, k) => k !== playerNum);
-        if (usedKeys.includes(key)) {
+        let isUsed = false;
+        for (let i = 1; i <= 4; i++) {
+          if (i !== playerNum && keyMappings[i] === key) {
+            isUsed = true;
+            break;
+          }
+        }
+        
+        if (isUsed) {
           alert(`Die Taste "${key}" ist bereits vergeben!`);
           input.value = keyMappings[playerNum];
+          input.blur();
           return;
         }
         
         keyMappings[playerNum] = key;
         input.value = key;
         input.blur();
-        document.removeEventListener('keydown', handleKeyPress);
       };
       
       document.addEventListener('keydown', handleKeyPress);