diff --git a/oh-my-zsh.sh b/oh-my-zsh.sh
index ddd1f043..a3ac5b76 100644
--- a/oh-my-zsh.sh
+++ b/oh-my-zsh.sh
@@ -54,3 +54,7 @@ else
   fi
 fi
 
+# Compile zcompdump, if modified, to increase startup speed.
+if [ "$HOME/.zcompdump" -nt "$HOME/.zcompdump.zwc" -o ! -e "$HOME/.zcompdump.zwc" ]; then
+  zcompile "$HOME/.zcompdump"
+fi