diff --git a/Codec/Sources/Codec/DataInput.swift b/Codec/Sources/Codec/DataInput.swift
index 178885ee..31455066 100644
--- a/Codec/Sources/Codec/DataInput.swift
+++ b/Codec/Sources/Codec/DataInput.swift
@@ -10,10 +10,10 @@ public protocol DataInput {
 
 extension DataInput {
     public mutating func read() throws -> UInt8 {
-        try read(length: 1)[0]
+        try read(length: 1).first!
     }
 
-    public mutating func decode() throws -> UInt64 {
+    public mutating func decodeUInt64() throws -> UInt64 {
         // TODO: improve this by use `read(minLength: 8)` to avoid read byte by byte
         let res = try IntegerCodec.decode { try self.read() }
         guard let res else {
diff --git a/Codec/Sources/Codec/JamDecoder.swift b/Codec/Sources/Codec/JamDecoder.swift
index 86ab169c..2e20e9de 100644
--- a/Codec/Sources/Codec/JamDecoder.swift
+++ b/Codec/Sources/Codec/JamDecoder.swift
@@ -100,7 +100,7 @@ private class DecodeContext: Decoder {
     }
 
     fileprivate func decodeData(codingPath: @autoclosure () -> [CodingKey]) throws -> Data {
-        let length = try input.decode()
+        let length = try input.decodeUInt64()
         // sanity check: length must be less than 4gb
         guard length < 0x1_0000_0000 else {
             throw DecodingError.dataCorrupted(
@@ -115,7 +115,7 @@ private class DecodeContext: Decoder {
     }
 
     fileprivate func decodeData(codingPath: @autoclosure () -> [CodingKey]) throws -> [UInt8] {
-        let length = try input.decode()
+        let length = try input.decodeUInt64()
         // sanity check: length must be less than 4gb
         guard length < 0x1_0000_0000 else {
             throw DecodingError.dataCorrupted(
@@ -130,7 +130,7 @@ private class DecodeContext: Decoder {
     }
 
     fileprivate func decodeArray<T: ArrayWrapper>(_ type: T.Type, key: CodingKey?) throws -> T {
-        let length = try input.decode()
+        let length = try input.decodeUInt64()
         // sanity check: length can't be unreasonably large
         guard length < 0xFFFFFF else {
             throw DecodingError.dataCorrupted(