diff --git a/docker.md b/docker.md
index 12800d8ca..eafad3fcb 100644
--- a/docker.md
+++ b/docker.md
@@ -43,7 +43,7 @@ docker create [options] IMAGE
   -i, --interactive          # attach stdin (interactive)
   -t, --tty                  # pseudo-tty
       --name NAME            # name your image
-  -p, --publish 5000:5000    # port map
+  -p, --publish 5000:5000    # port map (host:container)
       --expose 5432          # expose a port to linked containers
   -P, --publish-all          # publish all ports
       --link container:alias # linking