diff --git a/lib/internal/test_runner/coverage.js b/lib/internal/test_runner/coverage.js
index b97965235e7d47..7d78bd69886566 100644
--- a/lib/internal/test_runner/coverage.js
+++ b/lib/internal/test_runner/coverage.js
@@ -340,8 +340,8 @@ class TestCoverage {
       const { data, lineLengths } = sourceMapCache[url];
       let offset = 0;
       const executedLines = ArrayPrototypeMap(lineLengths, (length, i) => {
-        const coverageLine = new CoverageLine(i + 1, offset, null, length);
-        offset += length;
+        const coverageLine = new CoverageLine(i + 1, offset, null, length + 1);
+        offset += length + 1;
         return coverageLine;
       });
       if (data.sourcesContent != null) {
diff --git a/test/fixtures/test-runner/source-map-line-lengths/index.js b/test/fixtures/test-runner/source-map-line-lengths/index.js
new file mode 100644
index 00000000000000..ff63423bfb3c8b
--- /dev/null
+++ b/test/fixtures/test-runner/source-map-line-lengths/index.js
@@ -0,0 +1,77 @@
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+function a() {
+  console.log(1);
+}
+a();
+//# sourceMappingURL=index.js.map
diff --git a/test/fixtures/test-runner/source-map-line-lengths/index.js.map b/test/fixtures/test-runner/source-map-line-lengths/index.js.map
new file mode 100644
index 00000000000000..ace65dc3ccdd14
--- /dev/null
+++ b/test/fixtures/test-runner/source-map-line-lengths/index.js.map
@@ -0,0 +1,7 @@
+{
+  "version": 3,
+  "sources": ["index.ts"],
+  "sourcesContent": ["1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\n1;\nfunction a() {\n  console.log(1);\n}\na();\n"],
+  "mappings": "AAAA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA;AACA,SAAS,IAAI;AACX,UAAQ,IAAI,CAAC;AACf;AACA,EAAE;",
+  "names": []
+}
diff --git a/test/fixtures/test-runner/source-map-line-lengths/index.ts b/test/fixtures/test-runner/source-map-line-lengths/index.ts
new file mode 100644
index 00000000000000..0eee24b0c75e45
--- /dev/null
+++ b/test/fixtures/test-runner/source-map-line-lengths/index.ts
@@ -0,0 +1,76 @@
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+1;
+function a() {
+  console.log(1);
+}
+a();
diff --git a/test/parallel/test-runner-coverage.js b/test/parallel/test-runner-coverage.js
index 1283232a867246..8a6cb392de2585 100644
--- a/test/parallel/test-runner-coverage.js
+++ b/test/parallel/test-runner-coverage.js
@@ -428,3 +428,16 @@ test('coverage with included and excluded files', skipIfNoInspector, () => {
   assert.strictEqual(result.status, 0);
   assert(!findCoverageFileForPid(result.pid));
 });
+
+test('properly accounts for line endings in source maps', skipIfNoInspector, () => {
+  const fixture = fixtures.path('test-runner', 'source-map-line-lengths', 'index.js');
+  const args = [
+    '--test', '--experimental-test-coverage', '--test-reporter', 'tap',
+    fixture,
+  ];
+  const result = spawnSync(process.execPath, args);
+  const report = 'index.ts | 100.00 |   100.00 |  100.00 |';
+  assert.strictEqual(result.stderr.toString(), '');
+  assert(result.stdout.toString().includes(report));
+  assert.strictEqual(result.status, 0);
+});