diff --git a/evm/evm-codec/src/abi-components/function.ts b/evm/evm-codec/src/abi-components/function.ts
index 9c22d4e7e..2e9d31031 100644
--- a/evm/evm-codec/src/abi-components/function.ts
+++ b/evm/evm-codec/src/abi-components/function.ts
@@ -4,7 +4,7 @@ import { slotsCount } from "../utils";
 import { Src } from "../src";
 import assert from "node:assert";
 
-type FunctionReturn<T> = T extends Codec<infer U>
+type FunctionReturn<T> = T extends Codec<any, infer U>
   ? U
   : T extends Struct
   ? StructTypes<T>
diff --git a/evm/evm-codec/test/array.test.ts b/evm/evm-codec/test/array.test.ts
index 38e824aff..1737451e9 100644
--- a/evm/evm-codec/test/array.test.ts
+++ b/evm/evm-codec/test/array.test.ts
@@ -103,8 +103,8 @@ describe("dynamic size array", () => {
     ];
     const data2 = [[1n, 2n, 3n], [], [4n]];
     const data3 = [
-      [Buffer.from("1234", "hex"), Buffer.from("5678", "hex")],
-      [Buffer.from("dead", "hex"), Buffer.from("beef", "hex")],
+      ["0x1234", "0x5678"],
+      ["0xdead", "0xbeef"],
     ];
     arr1.encode(sink, data1);
     address.encode(sink, "0x1234567890123456789012345678901234567890");
diff --git a/evm/evm-codec/test/event.test.ts b/evm/evm-codec/test/event.test.ts
index f466dd635..904c4042a 100644
--- a/evm/evm-codec/test/event.test.ts
+++ b/evm/evm-codec/test/event.test.ts
@@ -60,9 +60,9 @@ describe("Event", () => {
       ),
     });
     expect(decoded).toEqual({
-      a: Buffer.from(topics[1].slice(2), "hex"),
+      a: topics[1],
       b: "hello",
-      c: Buffer.from([0x12, 0x34]),
+      c: "0x1234",
       d: { _0: 100n, _1: "world" },
       e: true,
     });
diff --git a/evm/evm-codec/test/function.test.ts b/evm/evm-codec/test/function.test.ts
index 8c821b5de..6d2f010ae 100644
--- a/evm/evm-codec/test/function.test.ts
+++ b/evm/evm-codec/test/function.test.ts
@@ -60,12 +60,12 @@ describe("Function", () => {
         bar: [1n, 2n, 3n],
         str: {
           foo: 123n,
-          bar: Buffer.from([0x12, 0x34, 0x56, 0x78]),
+          bar: "0x12345678" as const,
         },
       },
       arg4: {
         foo: 100n,
-        bar: Buffer.from([0x12, 0x34, 0x56, 0x78]),
+        bar: "0x12345678" as const,
       },
     };
     const viemArgs = [
diff --git a/evm/evm-codec/test/src.test.ts b/evm/evm-codec/test/src.test.ts
index 9f472dfe1..50c2f61aa 100644
--- a/evm/evm-codec/test/src.test.ts
+++ b/evm/evm-codec/test/src.test.ts
@@ -85,11 +85,9 @@ describe("src", () => {
     const src = new Src(encoded);
     expect(src.u8()).toBe(69);
     expect(src.string()).toBe(str1);
-    expect(src.staticBytes(7)).toStrictEqual(
-      Buffer.from(bytes7.slice(2), "hex")
-    );
+    expect(src.staticBytes(7)).toStrictEqual(bytes7);
     expect(src.i128()).toBe(-21312312452243312424534213123123123123n);
-    expect(src.bytes()).toStrictEqual(bytes1);
+    expect(src.bytes()).toStrictEqual("0x" + bytes1.toString("hex"));
     expect(src.address()).toBe(address);
     expect(src.string()).toBe(str2);
   });
@@ -132,6 +130,6 @@ describe("src", () => {
       "hex"
     );
     const src = new Src(encoded);
-    expect(src.bytes()).toStrictEqual(buffer);
+    expect(src.bytes()).toStrictEqual("0x" + buffer.toString("hex"));
   });
 });
diff --git a/evm/evm-codec/test/struct.bench.ts b/evm/evm-codec/test/struct.bench.ts
index 8cc8b9fb0..039c50d09 100644
--- a/evm/evm-codec/test/struct.bench.ts
+++ b/evm/evm-codec/test/struct.bench.ts
@@ -1,6 +1,6 @@
 import { bench, describe } from "vitest";
 import { address, array, Codec, Sink, Src, struct, uint256 } from "../src";
-import { decodeAbiParameters, encodeAbiParameters } from "viem";
+import { decodeAbiParameters, encodeAbiParameters, Hex } from "viem";
 import { ethers } from "ethers";
 
 const hugeArray = Array.from({ length: 1000 }, (_, i) => BigInt(i));
@@ -11,7 +11,7 @@ class InlinedStructCodec<
     b: bigint;
     c: {
       d: bigint[];
-      e: string;
+      e: Hex;
     };
   }
 > implements Codec<S>
diff --git a/evm/evm-codec/test/struct.test.ts b/evm/evm-codec/test/struct.test.ts
index ae36948f3..0189dcb9f 100644
--- a/evm/evm-codec/test/struct.test.ts
+++ b/evm/evm-codec/test/struct.test.ts
@@ -138,7 +138,7 @@ describe("StructCodec", () => {
       bar: [1n, 2n, 3n],
       str: {
         foo: 123n,
-        bar: Uint8Array.from([0x12, 0x34, 0x56, 0x78]),
+        bar: "0x12345678" as const,
       },
     });
     compareTypes(
@@ -177,7 +177,7 @@ describe("StructCodec", () => {
       bar: [1n, 2n, 3n],
       str: {
         foo: 123n,
-        bar: Buffer.from([0x12, 0x34, 0x56, 0x78]),
+        bar: "0x12345678",
       },
     });
   });