diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index 070e071290..dac85e0ace 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -971,6 +971,7 @@ static int lxcContainerMountFSBlockHelper(virDomainFSDefPtr fs,
     }
 
 cleanup:
+    VIR_FREE(format);
     return ret;
 }