diff --git a/test/doctool/test-doctool-html.js b/test/doctool/test-doctool-html.js
index 499034cd8a3684..703a7dcd21acb0 100644
--- a/test/doctool/test-doctool-html.js
+++ b/test/doctool/test-doctool-html.js
@@ -95,6 +95,10 @@ const testData = [
     html: '<ol><li>fish</li><li>fish</li></ol>' +
       '<ul><li>Red fish</li><li>Blue fish</li></ul>',
   },
+  {
+    file: fixtures.path('altdocs.md'),
+    html: '<li><a href="https://nodejs.org/docs/latest-v8.x/api/foo.html">8.x',
+  },
 ];
 
 const spaces = /\s/g;
@@ -117,7 +121,8 @@ testData.forEach(({ file, html }) => {
         const actual = output.replace(spaces, '');
         // Assert that the input stripped of all whitespace contains the
         // expected markup.
-        assert(actual.includes(expected));
+        assert(actual.includes(expected),
+               `ACTUAL: ${actual}\nEXPECTED: ${expected}`);
       })
     );
   }));
diff --git a/test/fixtures/altdocs.md b/test/fixtures/altdocs.md
new file mode 100644
index 00000000000000..f5320533ad699c
--- /dev/null
+++ b/test/fixtures/altdocs.md
@@ -0,0 +1,2 @@
+# ALTDOCS
+<!--introduced_in=v8.4.0-->
diff --git a/tools/doc/html.js b/tools/doc/html.js
index 9c9c355574d4e5..ce53bceaa24a15 100644
--- a/tools/doc/html.js
+++ b/tools/doc/html.js
@@ -427,6 +427,7 @@ function altDocs(filename, docCreated) {
     const [versionMajor, versionMinor] = version.num.split('.').map(Number);
     if (docCreatedMajor > versionMajor) return false;
     if (docCreatedMajor < versionMajor) return true;
+    if (Number.isNaN(versionMinor)) return true;
     return docCreatedMinor <= versionMinor;
   }