diff --git a/runon/runon.py b/runon/runon.py
index 9bd61e8..2d35055 100755
--- a/runon/runon.py
+++ b/runon/runon.py
@@ -202,12 +202,10 @@ def run_container(client, container):
 def main():
     osname = None
     run_name = os.path.basename(os.sys.argv[0])
-    if run_name == 'runos':
+    if run_name == "runon":
         pass
-    elif run_name.startswith('runon'):
-        m = re.match('runon[-_]?(.*)$', run_name)
-        if m:
-            osname = m[1]
+    elif run_name.startswith("runon_"):
+        osname = run_name[len("runon_"):]
     else:
         osname = run_name