diff --git a/packages/babel-core/src/transformation/file/index.js b/packages/babel-core/src/transformation/file/index.js
index 74098e6446..ab1f1e650e 100644
--- a/packages/babel-core/src/transformation/file/index.js
+++ b/packages/babel-core/src/transformation/file/index.js
@@ -391,7 +391,7 @@ export default class File extends Store {
           mergedGenerator.addMapping({
             source: mapping.source,
 
-            original: {
+            original: mapping.source == null ? null : {
               line: mapping.originalLine,
               column: mapping.originalColumn
             },
diff --git a/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/actual.js b/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/actual.js
new file mode 100644
index 0000000000..2c7d540acb
--- /dev/null
+++ b/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/actual.js
@@ -0,0 +1,5 @@
+var foo = function () {
+  return 4;
+};
+
+//# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIm9yaWdpbmFsLmpzIl0sIm5hbWVzIjpbXSwibWFwcGluZ3MiOiJBQUFBLFVBQVUsWTtTQUFNLEM7Q0FBQyIsInNvdXJjZXNDb250ZW50IjpbInZhciBmb28gPSAoKSA9PiA0OyJdfQ==
diff --git a/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/expected.js b/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/expected.js
new file mode 100644
index 0000000000..cf3efeceb3
--- /dev/null
+++ b/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/expected.js
@@ -0,0 +1,3 @@
+var foo = function () {
+  return 4;
+};
diff --git a/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/options.json b/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/options.json
new file mode 100644
index 0000000000..0e6084f210
--- /dev/null
+++ b/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/options.json
@@ -0,0 +1,3 @@
+{
+  "inputSourceMap": true
+}
diff --git a/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/source-map.json b/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/source-map.json
new file mode 100644
index 0000000000..ba7a5c1760
--- /dev/null
+++ b/packages/babel-core/test/fixtures/transformation/source-maps/input-source-map/source-map.json
@@ -0,0 +1,11 @@
+{
+  "version": 3,
+  "mappings": "AAAA;SAAgB,A,AAAC,E;CAAP",
+  "names": [],
+  "sources": [
+    "original.js"
+  ],
+  "sourcesContent": [
+    "var foo = () => 4;"
+  ]
+}