diff --git a/lib/interface-types/src/ast.rs b/lib/interface-types/src/ast.rs
index 8a7822175..b966f010e 100644
--- a/lib/interface-types/src/ast.rs
+++ b/lib/interface-types/src/ast.rs
@@ -1,13 +1,12 @@
 use std::str;
 
-#[derive(PartialEq, Debug)]
+#[derive(PartialEq, Clone, Copy, Debug)]
 pub enum InterfaceType {
     Int,
     Float,
     Any,
     String,
     Seq,
-
     I32,
     I64,
     F32,
@@ -35,7 +34,7 @@ pub enum Instruction<'input> {
     TableRefGet,
     CallMethod(u64),
     MakeRecord(InterfaceType),
-    GetField(u64, u64),
+    GetField(InterfaceType, u64),
     Const(InterfaceType, u64),
     FoldSeq(u64),
 }
diff --git a/lib/interface-types/src/decoders/binary.rs b/lib/interface-types/src/decoders/binary.rs
index 614b7b828..f3cedc53b 100644
--- a/lib/interface-types/src/decoders/binary.rs
+++ b/lib/interface-types/src/decoders/binary.rs
@@ -177,7 +177,7 @@ fn instructions<'input, E: ParseError<&'input [u8]>>(
         }
 
         0x0c => {
-            consume!((input, argument_0) = leb(input)?);
+            consume!((input, argument_0) = ty(input)?);
             consume!((input, argument_1) = leb(input)?);
             (input, Instruction::GetField(argument_0, argument_1))
         }
@@ -479,7 +479,7 @@ mod tests {
             0x08, // TableRefGet
             0x09, 0x01, // CallMethod(1)
             0x0a, 0x7f, // MakeRecord(I32)
-            0x0c, 0x01, 0x02, // GetField(1, 2)
+            0x0c, 0xff, 0xff, 0x01, 0x02, // GetField(Int, 2)
             0x0d, 0x7f, 0x01, // Const(I32, 1)
             0x0e, 0x01, // FoldSeq(1)
             0x0a,
@@ -498,7 +498,7 @@ mod tests {
                 Instruction::TableRefGet,
                 Instruction::CallMethod(1),
                 Instruction::MakeRecord(InterfaceType::I32),
-                Instruction::GetField(1, 2),
+                Instruction::GetField(InterfaceType::Int, 2),
                 Instruction::Const(InterfaceType::I32, 1),
                 Instruction::FoldSeq(1),
             ],
diff --git a/lib/interface-types/src/decoders/mod.rs b/lib/interface-types/src/decoders/mod.rs
new file mode 100644
index 000000000..96eab6681
--- /dev/null
+++ b/lib/interface-types/src/decoders/mod.rs
@@ -0,0 +1 @@
+pub mod binary;