diff --git a/import-maps/import-maps-base-url.sub.html b/import-maps/import-maps-base-url.sub.html
index 3e09aeff17b884..0a5f9c0beee76b 100644
--- a/import-maps/import-maps-base-url.sub.html
+++ b/import-maps/import-maps-base-url.sub.html
@@ -22,6 +22,11 @@
   testDynamicImport(importMap, baseURL, "bare/bare", "log:bare", "module");
   testDynamicImport(importMap, baseURL, "bare/bare", "log:bare",
       "text/javascript");
+
+  testStaticImportInjectBase(importMap, baseURL, "bare/bare", "log:bare");
+  testDynamicImportInjectBase(importMap, baseURL, "bare/bare", "log:bare", "module");
+  testDynamicImportInjectBase(importMap, baseURL, "bare/bare", "log:bare",
+      "text/javascript");
 });
 
 </script>
diff --git a/import-maps/resources/inject-base.js b/import-maps/resources/inject-base.js
new file mode 100644
index 00000000000000..4d469aec89c398
--- /dev/null
+++ b/import-maps/resources/inject-base.js
@@ -0,0 +1,3 @@
+const el = document.createElement("base");
+el.href = "{{GET[baseurl]}}";
+document.currentScript.after(el);
diff --git a/import-maps/resources/test-helper.js b/import-maps/resources/test-helper.js
index 64982584ceb1b5..78215b2d017ac8 100644
--- a/import-maps/resources/test-helper.js
+++ b/import-maps/resources/test-helper.js
@@ -173,6 +173,66 @@ function testDynamicImport(importMapString, importMapBaseURL, specifier, expecte
   `);
 }
 
+function testInIframeInjectBase(importMapString, importMapBaseURL, testScript) {
+  const iframe = document.createElement('iframe');
+  document.body.appendChild(iframe);
+  let content = `
+    <script src="/resources/testharness.js"></script>
+    <script src="/import-maps/resources/test-helper.js"></script>
+    <script src="/import-maps/resources/inject-base.js?pipe=sub&baseurl=${importMapBaseURL}"></script>
+  `;
+
+  if (importMapString) {
+    content += `
+      <script type="importmap">
+      ${importMapString}
+      </sc` + `ript>
+    `;
+  }
+  content += `
+    <body>
+    <script>
+    setup({ allow_uncaught_exception: true });
+    ${testScript}
+    </sc` + `ript>
+  `;
+  iframe.contentDocument.write(content);
+  iframe.contentDocument.close();
+  fetch_tests_from_window(iframe.contentWindow);
+}
+
+function testStaticImportInjectBase(importMapString, importMapBaseURL, specifier, expected) {
+  testInIframeInjectBase(importMapString, importMapBaseURL, `
+    const t = async_test("${specifier}: static import with inject <base>");
+    const handlers = getHandlers(t, "${specifier}", "${expected}");
+    const script = document.createElement("script");
+    script.setAttribute("type", "module");
+    script.setAttribute("src",
+        "/import-maps/static-import.py?url=" +
+        encodeURIComponent("${specifier}"));
+    script.addEventListener("load", handlers[Handler.ScriptLoadEvent]);
+    script.addEventListener("error", handlers[Handler.ScriptErrorEvent]);
+    window.addEventListener("error", handlers[Handler.WindowErrorEvent]);
+    document.body.appendChild(script);
+  `);
+}
+
+function testDynamicImportInjectBase(importMapString, importMapBaseURL, specifier, expected, type) {
+  testInIframeInjectBase(importMapString, importMapBaseURL, `
+    const t = async_test("${specifier}: dynamic import (from ${type}) with inject <base>");
+    const handlers = getHandlers(t, "${specifier}", "${expected}");
+    const script = document.createElement("script");
+    script.setAttribute("type", "${type}");
+    script.innerText =
+        "import(\\"${specifier}\\")" +
+        ".then(handlers[Handler.DynamicImportResolve], " +
+        "handlers[Handler.DynamicImportReject]);";
+    script.addEventListener("error",
+        t.unreached_func("top-level inline script shouldn't error"));
+    document.body.appendChild(script);
+  `);
+}
+
 function doTests(importMapString, importMapBaseURL, tests) {
   window.addEventListener("load", () => {
     for (const specifier in tests) {
