diff --git a/src/yunohost/certificate.py b/src/yunohost/certificate.py
index 5f8c7ff2..de21299d 100644
--- a/src/yunohost/certificate.py
+++ b/src/yunohost/certificate.py
@@ -666,7 +666,7 @@ def _name_selfCA():
 
 
 def _tail(n, filePath):
-    stdin, stdout = os.popen2("tail -n " + str(n) + " " + filePath)
+    stdin, stdout = os.popen2("tail -n %s '%s'" % (n, filePath))
     stdin.close()
     lines = stdout.readlines()
     stdout.close()