diff --git a/Dockerfile b/Dockerfile
index 11d66ef..6c8af85 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,6 +3,9 @@ MAINTAINER David Liu <email4dliu@gmail.com>
 
 LABEL Description="Do your C/C++ development in Docker container. Based on Ubuntu, and added build-essential and valgrind so you can use g++/gcc/gdb/valgrind."
 
+#update package files to ensure newest versions
+run apt-get update
+
 #adds gcc valgrind
 run apt-get install -y build-essential valgrind