diff --git a/src/bun.js/ModuleLoader.zig b/src/bun.js/ModuleLoader.zig
index 378a6bb5c2..c40da5ff99 100644
--- a/src/bun.js/ModuleLoader.zig
+++ b/src/bun.js/ModuleLoader.zig
@@ -1947,7 +1947,8 @@ export fn Bun__transpileVirtualModule(
 ) bool {
     jsc.markBinding(@src());
     const jsc_vm = globalObject.bunVM();
-    bun.assert(jsc_vm.plugin_runner != null);
+    // Plugin runner is not required for virtual modules created via build.module()
+    // bun.assert(jsc_vm.plugin_runner != null);
 
     var specifier_slice = specifier_ptr.toUTF8(jsc_vm.allocator);
     const specifier = specifier_slice.slice();
diff --git a/src/bun.js/bindings/BunPlugin.cpp b/src/bun.js/bindings/BunPlugin.cpp
index 3ca7f114f4..c0f830030a 100644
--- a/src/bun.js/bindings/BunPlugin.cpp
+++ b/src/bun.js/bindings/BunPlugin.cpp
@@ -150,9 +150,14 @@ static EncodedJSValue jsFunctionAppendVirtualModulePluginBody(JSC::JSGlobalObjec
 
     virtualModules->set(moduleId, JSC::Strong<JSC::JSObject> { vm, jsCast<JSC::JSObject*>(functionValue) });
 
-    global->requireMap()->remove(globalObject, moduleIdValue);
+    auto* requireMap = global->requireMap();
     RETURN_IF_EXCEPTION(scope, {});
-    global->esmRegistryMap()->remove(globalObject, moduleIdValue);
+    requireMap->remove(globalObject, moduleIdValue);
+    RETURN_IF_EXCEPTION(scope, {});
+
+    auto* esmRegistry = global->esmRegistryMap();
+    RETURN_IF_EXCEPTION(scope, {});
+    esmRegistry->remove(globalObject, moduleIdValue);
     RETURN_IF_EXCEPTION(scope, {});
 
     return JSValue::encode(callframe->thisValue());
diff --git a/src/bun.js/bindings/headers-handwritten.h b/src/bun.js/bindings/headers-handwritten.h
index b52e538af1..8d15002abd 100644
--- a/src/bun.js/bindings/headers-handwritten.h
+++ b/src/bun.js/bindings/headers-handwritten.h
@@ -225,18 +225,19 @@ const JSErrorCode JSErrorCodeUserErrorCode = 254;
 // Must be kept in sync.
 typedef uint8_t BunLoaderType;
 const BunLoaderType BunLoaderTypeNone = 254;
-const BunLoaderType BunLoaderTypeJSX = 0;
-const BunLoaderType BunLoaderTypeJS = 1;
-const BunLoaderType BunLoaderTypeTS = 2;
-const BunLoaderType BunLoaderTypeTSX = 3;
-const BunLoaderType BunLoaderTypeCSS = 4;
-const BunLoaderType BunLoaderTypeFILE = 5;
-const BunLoaderType BunLoaderTypeJSON = 6;
-const BunLoaderType BunLoaderTypeJSONC = 7;
-const BunLoaderType BunLoaderTypeTOML = 8;
-const BunLoaderType BunLoaderTypeWASM = 9;
-const BunLoaderType BunLoaderTypeNAPI = 10;
-const BunLoaderType BunLoaderTypeYAML = 18;
+// Must match api/schema.zig Loader enum values
+const BunLoaderType BunLoaderTypeJSX = 1;
+const BunLoaderType BunLoaderTypeJS = 2;
+const BunLoaderType BunLoaderTypeTS = 3;
+const BunLoaderType BunLoaderTypeTSX = 4;
+const BunLoaderType BunLoaderTypeCSS = 5;
+const BunLoaderType BunLoaderTypeFILE = 6;
+const BunLoaderType BunLoaderTypeJSON = 7;
+const BunLoaderType BunLoaderTypeJSONC = 8;
+const BunLoaderType BunLoaderTypeTOML = 9;
+const BunLoaderType BunLoaderTypeWASM = 10;
+const BunLoaderType BunLoaderTypeNAPI = 11;
+const BunLoaderType BunLoaderTypeYAML = 19;
 
 #pragma mark - Stream
 
diff --git a/test/regression/issue/12548.test.ts b/test/regression/issue/12548.test.ts
new file mode 100644
index 0000000000..09874cc53a
--- /dev/null
+++ b/test/regression/issue/12548.test.ts
@@ -0,0 +1,76 @@
+import { expect, test } from "bun:test";
+import { bunEnv, bunExe, tempDir } from "harness";
+
+test("issue #12548: TypeScript syntax should work with 'ts' loader in BunPlugin", async () => {
+  using dir = tempDir("issue-12548", {
+    "index.js": `
+      import plugin from "./plugin.js";
+
+      Bun.plugin(plugin);
+
+      // This should work with 'ts' loader
+      console.log(require('virtual-ts-module'));
+    `,
+    "plugin.js": `
+      export default {
+        setup(build) {
+          build.module('virtual-ts-module', () => ({
+            contents: "import { type TSchema } from '@sinclair/typebox'; export const test = 'works';",
+            loader: 'ts',
+          }));
+        },
+      };
+    `,
+  });
+
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "index.js"],
+    env: bunEnv,
+    cwd: String(dir),
+    stderr: "pipe",
+    stdout: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  expect(exitCode).toBe(0);
+  expect(stderr).toBe("");
+  expect(stdout).toContain('test: "works"');
+});
+
+test("issue #12548: TypeScript type imports work with 'ts' loader", async () => {
+  using dir = tempDir("issue-12548-type-imports", {
+    "index.js": `
+      Bun.plugin({
+        setup(build) {
+          build.module('test-module', () => ({
+            contents: \`
+              import { type TSchema } from '@sinclair/typebox';
+              type MyType = { a: number };
+              export type { MyType };
+              export const value = 42;
+            \`,
+            loader: 'ts',
+          }));
+        },
+      });
+
+      const mod = require('test-module');
+      console.log(JSON.stringify(mod));
+    `,
+  });
+
+  await using proc = Bun.spawn({
+    cmd: [bunExe(), "index.js"],
+    env: bunEnv,
+    cwd: String(dir),
+    stderr: "pipe",
+    stdout: "pipe",
+  });
+
+  const [stdout, stderr, exitCode] = await Promise.all([proc.stdout.text(), proc.stderr.text(), proc.exited]);
+
+  expect(exitCode).toBe(0);
+  expect(stderr).toBe("");
+  expect(stdout).toContain('{"value":42}');
+});