diff --git a/src/func.rs b/src/func.rs
index c3549ec..c686e36 100644
--- a/src/func.rs
+++ b/src/func.rs
@@ -2,7 +2,7 @@ use std::rc::Rc;
 use std::fmt;
 use std::collections::HashMap;
 use std::borrow::Cow;
-use parity_wasm::elements::{FunctionType, Local, Opcodes};
+use parity_wasm::elements::{Local, Opcodes};
 use {Error, Signature};
 use host::Externals;
 use runner::{prepare_function_args, FunctionContext, Interpreter};
diff --git a/src/global.rs b/src/global.rs
index 1e3947e..f277b0b 100644
--- a/src/global.rs
+++ b/src/global.rs
@@ -1,8 +1,9 @@
 use std::rc::Rc;
 use std::cell::Cell;
-use parity_wasm::elements::ValueType;
 use value::RuntimeValue;
 use Error;
+use types::ValueType;
+use parity_wasm::elements::{ValueType as EValueType};
 
 #[derive(Clone, Debug)]
 pub struct GlobalRef(Rc<GlobalInstance>);
@@ -56,4 +57,8 @@ impl GlobalInstance {
 	pub fn value_type(&self) -> ValueType {
 		self.val.get().value_type()
 	}
+
+	pub(crate) fn elements_value_type(&self) -> EValueType {
+		self.value_type().into_elements()
+	}
 }
diff --git a/src/imports.rs b/src/imports.rs
index 685e278..43ed232 100644
--- a/src/imports.rs
+++ b/src/imports.rs
@@ -1,5 +1,5 @@
 use std::collections::HashMap;
-use parity_wasm::elements::{FunctionType, GlobalType, MemoryType, TableType};
+use parity_wasm::elements::{GlobalType, MemoryType, TableType};
 use global::GlobalRef;
 use memory::MemoryRef;
 use func::FuncRef;
diff --git a/src/lib.rs b/src/lib.rs
index 7103cf1..4e7ead5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -97,8 +97,6 @@ impl From<::common::stack::Error> for Error {
 	}
 }
 
-use types::Signature;
-
 mod validation;
 mod common;
 mod memory;
@@ -123,3 +121,4 @@ pub use self::imports::{ModuleImportResolver, ImportResolver, ImportsBuilder};
 pub use self::module::{ModuleInstance, ModuleRef, ExternVal, NotStartedModuleRef};
 pub use self::global::{GlobalInstance, GlobalRef};
 pub use self::func::{FuncInstance, FuncRef};
+pub use self::types::{Signature, ValueType};
diff --git a/src/module.rs b/src/module.rs
index 859cbae..07d5659 100644
--- a/src/module.rs
+++ b/src/module.rs
@@ -3,7 +3,7 @@ use std::cell::RefCell;
 use std::fmt;
 use std::collections::HashMap;
 use std::borrow::Cow;
-use parity_wasm::elements::{External, FunctionType, InitExpr, Internal, Opcode, ResizableLimits, Type};
+use parity_wasm::elements::{External, InitExpr, Internal, Opcode, ResizableLimits, Type};
 use {Error, Signature, MemoryInstance, RuntimeValue, TableInstance};
 use imports::ImportResolver;
 use global::{GlobalInstance, GlobalRef};
@@ -165,7 +165,7 @@ impl ModuleInstance {
 		let instance = ModuleRef(Rc::new(ModuleInstance::default()));
 
 		for &Type::Function(ref ty) in module.type_section().map(|ts| ts.types()).unwrap_or(&[]) {
-			let signature = Rc::new(ty.clone().into());
+			let signature = Rc::new(Signature::from_elements(ty.clone()));
 			instance.push_signature(signature);
 		}
 
@@ -207,7 +207,7 @@ impl ModuleInstance {
 						instance.push_memory(memory.clone());
 					}
 					(&External::Global(ref gl), &ExternVal::Global(ref global)) => {
-						if gl.content_type() != global.value_type() {
+						if gl.content_type() != global.elements_value_type() {
 							return Err(Error::Instantiation(format!(
 								"Expect global with {:?} type, but provided global with {:?} type",
 								gl.content_type(),
@@ -386,7 +386,7 @@ impl ModuleInstance {
 					let &Type::Function(ref func_type) = types
 						.get(fn_ty_idx as usize)
 						.expect("Due to validation functions should have valid types");
-					let signature = func_type.clone().into();
+					let signature = Signature::from_elements(func_type.clone());
 					let func = imports.resolve_func(module_name, field_name, &signature)?;
 					ExternVal::Func(func)
 				}
diff --git a/src/runner.rs b/src/runner.rs
index f15d675..e36553a 100644
--- a/src/runner.rs
+++ b/src/runner.rs
@@ -4,7 +4,7 @@ use std::{u32, usize};
 use std::fmt::{self, Display};
 use std::iter::repeat;
 use std::collections::{HashMap, VecDeque};
-use parity_wasm::elements::{Opcode, BlockType, Local, FunctionType};
+use parity_wasm::elements::{Opcode, BlockType, Local};
 use {Error, Signature};
 use module::ModuleRef;
 use func::FuncRef;
@@ -1010,7 +1010,7 @@ impl FunctionContext {
 			is_initialized: false,
 			function: function,
 			module: module,
-			return_type: signature.return_type().map(|vt| BlockType::Value(vt)).unwrap_or(BlockType::NoResult),
+			return_type: signature.return_type().map(|vt| BlockType::Value(vt.into_elements())).unwrap_or(BlockType::NoResult),
 			value_stack: StackWithLimit::with_limit(value_stack_limit),
 			frame_stack: StackWithLimit::with_limit(frame_stack_limit),
 			locals: args,
@@ -1025,7 +1025,7 @@ impl FunctionContext {
 				FuncInstance::Host { .. } => panic!("Host functions can't be called as internally defined functions; Thus FunctionContext can be created only with internally defined functions; qed"),
 			};
 			let function_type = function.signature();
-			let function_return_type = function_type.return_type().map(|vt| BlockType::Value(vt)).unwrap_or(BlockType::NoResult);
+			let function_return_type = function_type.return_type().map(|vt| BlockType::Value(vt.into_elements())).unwrap_or(BlockType::NoResult);
 			let function_locals = prepare_function_args(&function_type, &mut self.value_stack)?;
 			(function_locals, module, function_return_type)
 		};
diff --git a/src/tests/host.rs b/src/tests/host.rs
index 58cbcd6..f76e9a2 100644
--- a/src/tests/host.rs
+++ b/src/tests/host.rs
@@ -1,11 +1,12 @@
 
-use parity_wasm::elements::{deserialize_buffer, FunctionType, MemoryType, TableType, ValueType};
+use parity_wasm::elements::{deserialize_buffer, MemoryType, TableType};
 use validation::{validate_module, ValidatedModule};
 use {
 	Error, Signature, Externals, FuncInstance, FuncRef, HostError, ImportsBuilder,
 	MemoryInstance, MemoryRef, TableInstance, TableRef, ModuleImportResolver, ModuleInstance, ModuleRef,
 	RuntimeValue, TryInto,
 };
+use types::ValueType;
 use wabt::wat2wasm;
 
 #[derive(Debug, Clone, PartialEq)]
diff --git a/src/tests/wasm.rs b/src/tests/wasm.rs
index 282bae9..22935a5 100644
--- a/src/tests/wasm.rs
+++ b/src/tests/wasm.rs
@@ -1,5 +1,5 @@
 use parity_wasm::elements::deserialize_file;
-use parity_wasm::elements::{FunctionType, GlobalType, MemoryType, Module, TableType};
+use parity_wasm::elements::{GlobalType, MemoryType, Module, TableType};
 use {Error, Signature, FuncRef, GlobalInstance, GlobalRef, ImportsBuilder, MemoryInstance,
                   MemoryRef, ModuleImportResolver, ModuleInstance, NopExternals, RuntimeValue,
                   TableInstance, TableRef};
diff --git a/src/types.rs b/src/types.rs
index 5fefceb..c5d770b 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -1,28 +1,59 @@
-use parity_wasm::elements::{FunctionType, ValueType};
+use parity_wasm::elements::{FunctionType, ValueType as EValueType};
 
 #[derive(Debug, Clone, PartialEq)]
 pub struct Signature {
-	func_type: FunctionType,
+	params: Vec<ValueType>,
+	return_type: Option<ValueType>,
 }
 
 impl Signature {
 	pub fn new(params: &[ValueType], return_type: Option<ValueType>) -> Signature {
 		Signature {
-			func_type: FunctionType::new(params.to_vec(), return_type),
+			params: params.to_vec(),
+			return_type: return_type,
 		}
 	}
 
 	pub fn params(&self) -> &[ValueType] {
-		self.func_type.params()
+		&self.params
 	}
 
 	pub fn return_type(&self) -> Option<ValueType> {
-		self.func_type.return_type()
+		self.return_type
+	}
+
+	pub(crate) fn from_elements(func_type: FunctionType) -> Signature {
+		Signature {
+			params: func_type.params().iter().cloned().map(ValueType::from_elements).collect(),
+			return_type: func_type.return_type().map(ValueType::from_elements),
+		}
 	}
 }
 
-impl From<FunctionType> for Signature {
-	fn from(func_type: FunctionType) -> Signature {
-		Signature { func_type }
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum ValueType {
+	I32,
+	I64,
+	F32,
+	F64,
+}
+
+impl ValueType {
+	pub(crate) fn from_elements(value_type: EValueType) -> ValueType {
+		match value_type {
+			EValueType::I32 => ValueType::I32,
+			EValueType::I64 => ValueType::I64,
+			EValueType::F32 => ValueType::F32,
+			EValueType::F64 => ValueType::F64,
+		}
+	}
+
+	pub(crate) fn into_elements(self) -> EValueType {
+		match self {
+			ValueType::I32 => EValueType::I32,
+			ValueType::I64 => EValueType::I64,
+			ValueType::F32 => EValueType::F32,
+			ValueType::F64 => EValueType::F64,
+		}
 	}
 }
diff --git a/src/value.rs b/src/value.rs
index 0b7c4ee..d426384 100644
--- a/src/value.rs
+++ b/src/value.rs
@@ -130,12 +130,12 @@ impl RuntimeValue {
 	}
 
 	/// Get variable type for this value.
-	pub fn value_type(&self) -> ValueType {
+	pub fn value_type(&self) -> ::types::ValueType {
 		match *self {
-			RuntimeValue::I32(_) => ValueType::I32,
-			RuntimeValue::I64(_) => ValueType::I64,
-			RuntimeValue::F32(_) => ValueType::F32,
-			RuntimeValue::F64(_) => ValueType::F64,
+			RuntimeValue::I32(_) => ::types::ValueType::I32,
+			RuntimeValue::I64(_) => ::types::ValueType::I64,
+			RuntimeValue::F32(_) => ::types::ValueType::F32,
+			RuntimeValue::F64(_) => ::types::ValueType::F64,
 		}
 	}
 }