src/java.base/share/classes/java/lang/StringBuilder.java

@@ -411,11 +411,11 @@
     @Override
     @HotSpotIntrinsicCandidate
     public String toString() {
         // Create a copy, don't share the array
         return isLatin1() ? StringLatin1.newString(value, 0, count)
-                          : StringUTF16.newStringSB(value, 0, count);
+                          : StringUTF16.newString(value, 0, count);
     }
 
     /**
      * Save the state of the {@code StringBuilder} instance to a stream
      * (that is, serialize it).