diff --git a/es/blatt3/uebung3-4/uebung3-4.ino b/es/blatt3/uebung3-4/uebung3-4.ino
index 6651c2f..eafdb54 100644
--- a/es/blatt3/uebung3-4/uebung3-4.ino
+++ b/es/blatt3/uebung3-4/uebung3-4.ino
@@ -94,7 +94,7 @@ void loop() {
       bool readable = true;
       while (readable) {
         currentChar = Serial.read();
-        readable = (currentChar == -1);
+        readable = (currentChar != -1);
         command[i] = currentChar;
         i++;
       }