diff --git a/src/Decoder.ts b/src/Decoder.ts
index e9257a9..9239dd1 100644
--- a/src/Decoder.ts
+++ b/src/Decoder.ts
@@ -1,4 +1,3 @@
-import "./utils/symbol.dispose.ts";
 import { prettyByte } from "./utils/prettyByte.ts";
 import { ExtensionCodec, ExtensionCodecType } from "./ExtensionCodec.ts";
 import { getInt64, getUint64, UINT32_MAX } from "./utils/int.ts";
@@ -305,15 +304,6 @@ export class Decoder<ContextType = undefined> {
     return new RangeError(`Extra ${view.byteLength - pos} of ${view.byteLength} byte(s) found at buffer[${posToShow}]`);
   }
 
-  private enteringGuard(): Disposable {
-    this.entered = true;
-    return {
-      [Symbol.dispose]: () => {
-        this.entered = false;
-      },
-    };
-  }
-
   /**
    * @throws {@link DecodeError}
    * @throws {@link RangeError}
@@ -323,17 +313,21 @@ export class Decoder<ContextType = undefined> {
       const instance = this.clone();
       return instance.decode(buffer);
     }
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    using _guard = this.enteringGuard();
 
-    this.reinitializeState();
-    this.setBuffer(buffer);
+    try {
+      this.entered = true;
 
-    const object = this.doDecodeSync();
-    if (this.hasRemaining(1)) {
-      throw this.createExtraByteError(this.pos);
+      this.reinitializeState();
+      this.setBuffer(buffer);
+
+      const object = this.doDecodeSync();
+      if (this.hasRemaining(1)) {
+        throw this.createExtraByteError(this.pos);
+      }
+      return object;
+    } finally {
+      this.entered = false;
     }
-    return object;
   }
 
   public *decodeMulti(buffer: ArrayLike<number> | ArrayBufferView | ArrayBufferLike): Generator<unknown, void, unknown> {
@@ -342,14 +336,18 @@ export class Decoder<ContextType = undefined> {
       yield* instance.decodeMulti(buffer);
       return;
     }
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    using _guard = this.enteringGuard();
 
-    this.reinitializeState();
-    this.setBuffer(buffer);
+    try {
+      this.entered = true;
 
-    while (this.hasRemaining(1)) {
-      yield this.doDecodeSync();
+      this.reinitializeState();
+      this.setBuffer(buffer);
+
+      while (this.hasRemaining(1)) {
+        yield this.doDecodeSync();
+      }
+    } finally {
+      this.entered = false;
     }
   }
 
@@ -358,42 +356,46 @@ export class Decoder<ContextType = undefined> {
       const instance = this.clone();
       return instance.decodeAsync(stream);
     }
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    using _guard = this.enteringGuard();
 
-    let decoded = false;
-    let object: unknown;
-    for await (const buffer of stream) {
-      if (decoded) {
-        this.entered = false;
-        throw this.createExtraByteError(this.totalPos);
-      }
+    try {
+      this.entered = true;
 
-      this.appendBuffer(buffer);
+      let decoded = false;
+      let object: unknown;
+      for await (const buffer of stream) {
+        if (decoded) {
+          this.entered = false;
+          throw this.createExtraByteError(this.totalPos);
+        }
 
-      try {
-        object = this.doDecodeSync();
-        decoded = true;
-      } catch (e) {
-        if (!(e instanceof RangeError)) {
-          throw e; // rethrow
+        this.appendBuffer(buffer);
+
+        try {
+          object = this.doDecodeSync();
+          decoded = true;
+        } catch (e) {
+          if (!(e instanceof RangeError)) {
+            throw e; // rethrow
+          }
+          // fallthrough
         }
-        // fallthrough
+        this.totalPos += this.pos;
       }
-      this.totalPos += this.pos;
-    }
 
-    if (decoded) {
-      if (this.hasRemaining(1)) {
-        throw this.createExtraByteError(this.totalPos);
+      if (decoded) {
+        if (this.hasRemaining(1)) {
+          throw this.createExtraByteError(this.totalPos);
+        }
+        return object;
       }
-      return object;
-    }
 
-    const { headByte, pos, totalPos } = this;
-    throw new RangeError(
-      `Insufficient data in parsing ${prettyByte(headByte)} at ${totalPos} (${pos} in the current buffer)`,
-    );
+      const { headByte, pos, totalPos } = this;
+      throw new RangeError(
+        `Insufficient data in parsing ${prettyByte(headByte)} at ${totalPos} (${pos} in the current buffer)`,
+      );
+    } finally {
+      this.entered = false;
+    }
   }
 
   public decodeArrayStream(
@@ -412,39 +414,43 @@ export class Decoder<ContextType = undefined> {
       yield* instance.decodeMultiAsync(stream, isArray);
       return;
     }
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    using _guard = this.enteringGuard();
 
-    let isArrayHeaderRequired = isArray;
-    let arrayItemsLeft = -1;
+    try {
+      this.entered = true;
 
-    for await (const buffer of stream) {
-      if (isArray && arrayItemsLeft === 0) {
-        throw this.createExtraByteError(this.totalPos);
-      }
+      let isArrayHeaderRequired = isArray;
+      let arrayItemsLeft = -1;
 
-      this.appendBuffer(buffer);
+      for await (const buffer of stream) {
+        if (isArray && arrayItemsLeft === 0) {
+          throw this.createExtraByteError(this.totalPos);
+        }
 
-      if (isArrayHeaderRequired) {
-        arrayItemsLeft = this.readArraySize();
-        isArrayHeaderRequired = false;
-        this.complete();
-      }
+        this.appendBuffer(buffer);
 
-      try {
-        while (true) {
-          yield this.doDecodeSync();
-          if (--arrayItemsLeft === 0) {
-            break;
-          }
+        if (isArrayHeaderRequired) {
+          arrayItemsLeft = this.readArraySize();
+          isArrayHeaderRequired = false;
+          this.complete();
         }
-      } catch (e) {
-        if (!(e instanceof RangeError)) {
-          throw e; // rethrow
+
+        try {
+          while (true) {
+            yield this.doDecodeSync();
+            if (--arrayItemsLeft === 0) {
+              break;
+            }
+          }
+        } catch (e) {
+          if (!(e instanceof RangeError)) {
+            throw e; // rethrow
+          }
+          // fallthrough
         }
-        // fallthrough
+        this.totalPos += this.pos;
       }
-      this.totalPos += this.pos;
+    } finally {
+      this.entered = false;
     }
   }
 
diff --git a/src/Encoder.ts b/src/Encoder.ts
index 27d8ded..ffb4f6b 100644
--- a/src/Encoder.ts
+++ b/src/Encoder.ts
@@ -1,4 +1,3 @@
-import "./utils/symbol.dispose.ts";
 import { utf8Count, utf8Encode } from "./utils/utf8.ts";
 import { ExtensionCodec, ExtensionCodecType } from "./ExtensionCodec.ts";
 import { setInt64, setUint64 } from "./utils/int.ts";
@@ -127,15 +126,6 @@ export class Encoder<ContextType = undefined> {
     this.pos = 0;
   }
 
-  private enteringGuard(): Disposable {
-    this.entered = true;
-    return {
-      [Symbol.dispose]: () => {
-        this.entered = false;
-      },
-    };
-  }
-
   /**
    * This is almost equivalent to {@link Encoder#encode}, but it returns an reference of the encoder's internal buffer and thus much faster than {@link Encoder#encode}.
    *
@@ -146,12 +136,16 @@ export class Encoder<ContextType = undefined> {
       const instance = this.clone();
       return instance.encodeSharedRef(object);
     }
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    using _guard = this.enteringGuard();
 
-    this.reinitializeState();
-    this.doEncode(object, 1);
-    return this.bytes.subarray(0, this.pos);
+    try {
+      this.entered = true;
+
+      this.reinitializeState();
+      this.doEncode(object, 1);
+      return this.bytes.subarray(0, this.pos);
+    } finally {
+      this.entered = false;
+    }
   }
 
   /**
@@ -162,12 +156,16 @@ export class Encoder<ContextType = undefined> {
       const instance = this.clone();
       return instance.encode(object);
     }
-    // eslint-disable-next-line @typescript-eslint/no-unused-vars
-    using _guard = this.enteringGuard();
 
-    this.reinitializeState();
-    this.doEncode(object, 1);
-    return this.bytes.slice(0, this.pos);
+    try {
+      this.entered = true;
+
+      this.reinitializeState();
+      this.doEncode(object, 1);
+      return this.bytes.slice(0, this.pos);
+    } finally {
+      this.entered = false;
+    }
   }
 
   private doEncode(object: unknown, depth: number): void {
diff --git a/src/utils/symbol.dispose.ts b/src/utils/symbol.dispose.ts
deleted file mode 100644
index d5d1eba..0000000
--- a/src/utils/symbol.dispose.ts
+++ /dev/null
@@ -1,11 +0,0 @@
-// 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,
-  });
-}