diff --git a/CHANGELOG.md b/CHANGELOG.md
index e59f87d0..183a0a16 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 - Set loglevel to debug for some message. [#159](https://github.com/greenbone/ospd/pull/159)
+- Improve error handling when stop a scan. [#163](https://github.com/greenbone/ospd/pull/163)
 
 ### Fixed
 - Fix set permission in unix socket. [#157](https://github.com/greenbone/ospd/pull/157)
diff --git a/ospd/ospd.py b/ospd/ospd.py
index 8f203bb6..7ad6ae82 100644
--- a/ospd/ospd.py
+++ b/ospd/ospd.py
@@ -659,7 +659,12 @@ def stop_scan(self, scan_id):
         except AttributeError:
             logger.debug('%s: The scanner task stopped unexpectedly.', scan_id)
 
-        os.killpg(os.getpgid(scan_process.ident), 15)
+        try:
+            os.killpg(os.getpgid(scan_process.ident), 15)
+        except ProcessLookupError as e:
+            logger.info('%s: Scan already stopped %s.',
+                        scan_id, scan_process.ident)
+
         if scan_process.ident != os.getpid():
             scan_process.join()
         logger.info('%s: Scan stopped.', scan_id)