diff --git a/woff2/build.sh b/woff2/build.sh
index 2fa2d982c..d4fb2b3f6 100755
--- a/woff2/build.sh
+++ b/woff2/build.sh
@@ -17,6 +17,9 @@
 
 cd /src/woff2
 
+# Checkout and update submodules.
+git submodule update --init --recursive
+
 # Build the library. Actually there is no 'library' target, so we use .o files.
 # '-no-canonical-prefixes' flag makes clang crazy. Need to avoid it.
 cat brotli/shared.mk | sed -e "s/-no-canonical-prefixes//" \