diff --git a/tools/releasetools/build_image.py b/tools/releasetools/build_image.py
index cbcad6d..b12969e 100755
--- a/tools/releasetools/build_image.py
+++ b/tools/releasetools/build_image.py
@@ -31,7 +31,7 @@
 FIXED_SALT = "aee087a5be3b982978c923f566a94613496b417f2af592639bc80d141e34dfe7"
 
 def RunCommand(cmd):
-  """ Echo and run the given command
+  """ Echo and run the given command.
 
   Args:
     cmd: the command represented as a list of strings.