Add submodule notice to README.md

1 files changed, 6 insertions, 0 deletions

diff --git a/README.md b/README.md
index 703a9d8..6d21e4f 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,12 @@ It's turing complete and somewhat useable.
 
 ## Invocation
 
+Make sure the submodules are checked out:
+
+```
+git submodule update --init
+```
+
 To build:
 
 ```