diff --git a/src/Decoder.ts b/src/Decoder.ts
index 55109d2..3a40f9e 100644
--- a/src/Decoder.ts
+++ b/src/Decoder.ts
@@ -1,3 +1,4 @@
+import "./utils/symbol.dispose";
 import { prettyByte } from "./utils/prettyByte";
 import { ExtensionCodec, ExtensionCodecType } from "./ExtensionCodec";
 import { getInt64, getUint64, UINT32_MAX } from "./utils/int";
diff --git a/src/Encoder.ts b/src/Encoder.ts
index af32b33..393c275 100644
--- a/src/Encoder.ts
+++ b/src/Encoder.ts
@@ -1,3 +1,4 @@
+import "./utils/symbol.dispose";
 import { utf8Count, utf8Encode } from "./utils/utf8";
 import { ExtensionCodec, ExtensionCodecType } from "./ExtensionCodec";
 import { setInt64, setUint64 } from "./utils/int";
diff --git a/src/utils/symbol.dispose.ts b/src/utils/symbol.dispose.ts
new file mode 100644
index 0000000..d5d1eba
--- /dev/null
+++ b/src/utils/symbol.dispose.ts
@@ -0,0 +1,11 @@
+// Polyfill to Symbol.dispose
+
+// eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
+if (!Symbol.dispose) {
+  Object.defineProperty(Symbol, "dispose", {
+    value: Symbol("dispose"),
+    writable: false,
+    enumerable: false,
+    configurable: false,
+  });
+}
diff --git a/tools/esmify.ts b/tools/esmify.ts
index ce57795..8447c10 100644
--- a/tools/esmify.ts
+++ b/tools/esmify.ts
@@ -11,6 +11,7 @@ for (const file of files) {
   // .js => .mjs
   const content = fs.readFileSync(file).toString("utf-8");
   const newContent = content.replace(/\bfrom "(\.\.?\/[^"]+)";/g, 'from "$1.mjs";')
+    .replace(/\bimport "(\.\.?\/[^"]+)";/g, 'import "$1.mjs";')
     .replace(/\/\/# sourceMappingURL=(.+)\.js\.map$/,
       "//# sourceMappingURL=$1.mjs.map");
   fs.writeFileSync(fileMjs, newContent);