--- 
+++ 
@@ -22,6 +22,7 @@
         if(this.runningState != STATE_RUNNING && this.runningState != STATE_SUSPENDED) {
             throw new IllegalStateException("Stopwatch is not running. ");
         }
+        if(this.runningState == STATE_RUNNING)
             stopTime = System.currentTimeMillis();
         this.runningState = STATE_STOPPED;
     }