diff --git a/lib/main.js b/lib/main.js
index 6e200ad..25692da 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -105,6 +105,7 @@ function run() {
             const inDownstreamModOptions = Object.assign(Object.assign({}, inDownstreamOptions), { cwd: downstreamModDirFull });
             yield (0, exec_1.exec)("git", ["clone", "--quiet", downstreamRepo, downstreamDir]);
             yield (0, exec_1.exec)("git", ["checkout", "-b", branchName], inDownstreamOptions);
+            yield (0, exec_1.exec)("git", ["submodule", "update", "--init"], inDownstreamOptions);
             yield (0, exec_1.exec)("git", ["config", "user.name", gitUser], inDownstreamOptions);
             yield (0, exec_1.exec)("git", ["config", "user.email", gitEmail], inDownstreamOptions);
             for (const replace of replacements) {
diff --git a/src/main.ts b/src/main.ts
index c7b4838..1507019 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -96,6 +96,8 @@ async function run() {
         await exec("git", ["clone", "--quiet", downstreamRepo, downstreamDir]);
 
         await exec("git", ["checkout", "-b", branchName], inDownstreamOptions);
+        await exec("git", ["submodule", "update", "--init"], inDownstreamOptions);
+
         await exec("git", ["config", "user.name", gitUser], inDownstreamOptions);
         await exec("git", ["config", "user.email", gitEmail], inDownstreamOptions);