diff --git a/src/_transformations/specifiers.test.ts b/src/_transformations/specifiers.test.ts
index 149ea80..b6f6934 100644
--- a/src/_transformations/specifiers.test.ts
+++ b/src/_transformations/specifiers.test.ts
@@ -1,6 +1,12 @@
 import fc from "https://esm.sh/fast-check@3.10.0";
-import { name, services, transpileSpecifier } from "./specifiers.ts";
+import {
+  name,
+  services,
+  transpileHttpsImport,
+  transpileSpecifier,
+} from "./specifiers.ts";
 
+const runtime = fc.stringMatching(/^\w+$/);
 const join = (array: string[]) => array.join("");
 const relativePrefix = fc.constantFrom("./", "../");
 const extension = fc.constantFrom("js", "ts", "jsx", "tsx");
@@ -20,9 +26,15 @@ Deno.test(function localSpecifiers() {
     fc.property(
       relativePath,
       extension,
-      (path, ext) =>
-        transpileSpecifier(`${path}.deno.m${ext}`) === `${path}.node.mjs` &&
-        transpileSpecifier(`${path}.deno.${ext}`) === `${path}.node.js`,
+      runtime,
+      runtime,
+      (path, ext, oldRuntime, newRuntime) => {
+        const fn = transpileSpecifier(oldRuntime, newRuntime);
+        return (
+          fn(`${path}.${oldRuntime}.m${ext}`) === `${path}.${newRuntime}.mjs` &&
+          fn(`${path}.${oldRuntime}.${ext}`) === `${path}.${newRuntime}.js`
+        );
+      },
     ),
   );
 });
@@ -31,7 +43,7 @@ Deno.test(function remoteSpecifiers() {
   fc.assert(
     fc.property(urlSegments, (segments) => {
       const [, scopedPackage, , path] = segments;
-      return transpileSpecifier(join(segments)) === scopedPackage + path;
+      return transpileHttpsImport(join(segments)) === scopedPackage + path;
     }),
   );
 });
diff --git a/src/_transformations/specifiers.ts b/src/_transformations/specifiers.ts
index a34f350..bfb3324 100644
--- a/src/_transformations/specifiers.ts
+++ b/src/_transformations/specifiers.ts
@@ -7,30 +7,30 @@ const version = /^@[^/?]+$/;
 const path = /\/[^?]*/;
 const url = re.tag()`^${re.union(services)}(${name})${version}?(${path})?.*$`;
 
-const transpileHttpsImport = (specifier: string) =>
+export const transpileHttpsImport = (specifier: string) =>
   specifier.replace(url, "$1$2");
 
 export const transpileExtension = (specifier: string) =>
   specifier.replace(/[jt]sx?$/i, "js");
 
-const transpileRelativeImport = (specifier: string) =>
-  transpileExtension(specifier).replace(".deno.", ".node.");
-
 const isRelative = (specifier: string) => /^\.\.?\//.test(specifier);
 
-export const transpileSpecifier = (specifier: string) => {
-  if (isRelative(specifier)) return transpileRelativeImport(specifier);
-  return transpileHttpsImport(specifier);
-};
+export const transpileSpecifier =
+  (oldRuntime: string, newRuntime: string) => (specifier: string) =>
+    isRelative(specifier)
+      ? transpileExtension(specifier).replace(
+        `.${oldRuntime}.`,
+        `.${newRuntime}.`,
+      )
+      : transpileHttpsImport(specifier);
 
 /**
  * Replaces all import/export specifiers in `sourceFile`
- * according to the specified `transpileSpecifier` function.
- * The default one makes specifiers Node-friendly.
+ * according to the specified `fn`.
  */
-export function transpileSpecifiers(
+export function replaceSpecifiers(
   sourceFile: SourceFile,
-  fn = transpileSpecifier,
+  fn: (specifier: string) => string,
 ) {
   for (const statement of sourceFile.getStatements()) {
     if (
diff --git a/src/context.ts b/src/context.ts
index 02cef58..0fb35f7 100644
--- a/src/context.ts
+++ b/src/context.ts
@@ -1,4 +1,8 @@
 import path from "node:path";
+import {
+  replaceSpecifiers,
+  transpileSpecifier,
+} from "./_transformations/specifiers.ts";
 import { type Config, parse } from "./config.ts";
 import { Project, ts } from "./deps.deno.ts";
 
@@ -18,6 +22,7 @@ export class Context {
   public baseDir: string;
   public config: Config;
   readonly project: Project;
+  private _runtime = "deno";
 
   /**
    * Synchronously loads `tsconfig.json` and `"files"`.
@@ -42,4 +47,20 @@ export class Context {
   resolve(...pathSegments: string[]) {
     return path.join(this.baseDir, ...pathSegments);
   }
+
+  changeRuntimeTo(newRuntime: string) {
+    const label = `Changing runtime from ${this._runtime} to ${newRuntime}`;
+    const fn = transpileSpecifier(this._runtime, newRuntime);
+
+    console.time(label);
+    for (const sourceFile of this.project.getSourceFiles()) {
+      if (sourceFile.getBaseName().includes(`.${this._runtime}.`)) {
+        sourceFile.forget();
+      } else {
+        replaceSpecifiers(sourceFile, fn);
+      }
+    }
+    this._runtime = newRuntime;
+    console.timeEnd(label);
+  }
 }
diff --git a/src/deno2node.ts b/src/deno2node.ts
index 0a54e91..be084a5 100644
--- a/src/deno2node.ts
+++ b/src/deno2node.ts
@@ -1,11 +1,6 @@
 import { shimEverything } from "./_transformations/shim.ts";
-import { transpileSpecifiers } from "./_transformations/specifiers.ts";
 import { vendorEverything } from "./_transformations/vendor.ts";
 import { type Context } from "./context.ts";
-import { type SourceFile } from "./deps.deno.ts";
-
-const isDenoSpecific = (sourceFile: SourceFile) =>
-  sourceFile.getBaseNameWithoutExtension().toLowerCase().endsWith(".deno");
 
 /**
  * Attempts to transform arbitrary `ctx.project` into a valid Node.js project:
@@ -44,16 +39,7 @@ const isDenoSpecific = (sourceFile: SourceFile) =>
  * [shim file]: https://github.com/fromdeno/deno2node/blob/main/src/shim.node.ts
  */
 export function deno2node(ctx: Context): void {
-  console.time("Basic transformations");
-  for (const sourceFile of ctx.project.getSourceFiles()) {
-    if (isDenoSpecific(sourceFile)) {
-      ctx.project.removeSourceFile(sourceFile);
-      continue;
-    }
-    transpileSpecifiers(sourceFile);
-  }
-  console.timeEnd("Basic transformations");
-
+  ctx.changeRuntimeTo("node");
   vendorEverything(ctx);
   shimEverything(ctx);
 }