diff --git a/CHANGELOG.md b/CHANGELOG.md
index bf6748057..8f2f23014 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,8 @@
 # Changelog
 
+## 9.5.1
+* [fix: inputSourceMap can be null](https://github.com/TypeStrong/ts-loader/pull/1639) [#1638] - thanks @johnnyreilly and @michaeltford
+
 ## 9.5.0
 * [Feature: map the input source map in case ts-loader is used in a loader pipeline](https://github.com/TypeStrong/ts-loader/pull/1626) - thanks @Ka0o0 and @bojanv55
 
diff --git a/package.json b/package.json
index 6a5e3f9f9..9bb7deced 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "ts-loader",
-  "version": "9.5.0",
+  "version": "9.5.1",
   "description": "TypeScript loader for webpack",
   "main": "index.js",
   "types": "dist",
diff --git a/src/index.ts b/src/index.ts
index ea950b779..c4c1b948c 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -149,7 +149,7 @@ function makeSourceMapAndFinish(
   // in the first case, we simply return undefined.
   // in the second case we only need to return the newly generated source map
   // this avoids that we have to make a possibly expensive call to the source-map lib
-  if (sourceMap === undefined || inputSourceMap === undefined) {
+  if (sourceMap === undefined || !inputSourceMap) {
     callback(null, output, sourceMap);
     return;
   }