diff --git a/overviewer.py b/overviewer.py
index 2f85384..a1cb800 100755
--- a/overviewer.py
+++ b/overviewer.py
@@ -140,6 +140,9 @@ def main():
         return 0
 
     if options.pid:
+		if os.path.exists(options.pid):
+			print("Already running (pid exists) - exiting..")
+			return 0
         with open(options.pid,"w") as f:
             f.write(str(os.getpid()))
     # if --check-terrain was specified, but we have NO config file, then we cannot