diff --git a/include/nbind/api.h b/include/nbind/api.h
index ceb4015..7f93a67 100644
--- a/include/nbind/api.h
+++ b/include/nbind/api.h
@@ -93,6 +93,7 @@ class Status {
 #	include "em/External.h"
 #	include "em/Callback.h"
 #	include "em/BindingStd.h"
+#	include "em/StdFunction.h"
 #	include "Buffer.h"
 #	include "em/Buffer.h"
 
diff --git a/include/nbind/em/Callback.h b/include/nbind/em/Callback.h
index aa346da..290035b 100644
--- a/include/nbind/em/Callback.h
+++ b/include/nbind/em/Callback.h
@@ -9,15 +9,26 @@
 
 namespace nbind {
 
-class cbFunction {
+// Wrapper class to specialize call function for different return types,
+// since function template partial specialization is forbidden.
+template <typename ReturnType>
+struct cbCaller {
+	typedef typename TypeTransformer<ReturnType>::Binding ReturnBindingType;
+
+	template <typename... Args>
+	static ReturnType call(unsigned int num, Args... args);
+};
+
+template <typename DefaultReturnType>
+class cbWrapper {
 
 public:
 
-	explicit cbFunction(unsigned int num = 0) : handle(num) {}
+	explicit cbWrapper(unsigned int num = 0) : handle(num) {}
 
 	template<typename... Args>
-	void operator()(Args&&... args) {
-		call<void>(std::forward<Args>(args)...);
+	DefaultReturnType operator()(Args&&... args) {
+		return(call<DefaultReturnType>(std::forward<Args>(args)...));
 	}
 
 	template <typename ReturnType, typename... Args>
@@ -25,28 +36,20 @@ class cbFunction {
 		// Restore linear allocator state in RAII style when done.
 		PoolRestore restore;
 
-		return(Caller<ReturnType>::call(handle.getNum(), std::forward<Args>(args)...));
+		return(cbCaller<ReturnType>::call(handle.getNum(), std::forward<Args>(args)...));
 	}
 
 private:
 
-	// Wrapper class to specialize call function for different return types,
-	// since function template partial specialization is forbidden.
-	template <typename ReturnType>
-	struct Caller {
-		typedef typename TypeTransformer<ReturnType>::Binding ReturnBindingType;
-
-		template <typename... Args>
-		static ReturnType call(unsigned int num, Args... args);
-	};
-
-	template<typename... Args>
-	static double callDouble(unsigned int num, Args... args);
-
 	External handle;
 
 };
 
+template<> template<typename... Args>
+void cbWrapper<void> :: operator()(Args&&... args) {
+	call<void>(std::forward<Args>(args)...);
+}
+
 class cbOutput {
 
 	template<typename ArgType>
@@ -81,8 +84,8 @@ class cbOutput {
 
 };
 
-template<typename... Args>
-double cbFunction::callDouble(unsigned int num, Args... args) {
+template <typename... Args>
+double callDouble(unsigned int num, Args... args) {
 	return(EM_ASM_DOUBLE(
 		{return(_nbind.callbackSignatureList[$0].apply(this,arguments));},
 		CallbackSignature<double, Args...>::getInstance().getNum(),
@@ -92,7 +95,7 @@ double cbFunction::callDouble(unsigned int num, Args... args) {
 }
 
 template <typename ReturnType> template <typename... Args>
-ReturnType cbFunction::Caller<ReturnType>::call(unsigned int num, Args... args) {
+ReturnType cbCaller<ReturnType>::call(unsigned int num, Args... args) {
 	return(ReturnBindingType::fromWireType(reinterpret_cast<typename ReturnBindingType::WireType>(
 		EM_ASM_INT(
 			{return(_nbind.callbackSignatureList[$0].apply(this,arguments));},
@@ -103,7 +106,7 @@ ReturnType cbFunction::Caller<ReturnType>::call(unsigned int num, Args... args)
 	)));
 }
 
-template<> struct cbFunction::Caller<void> {
+template<> struct cbCaller<void> {
 
 	template <typename... Args>
 	static void call(unsigned int num, Args... args) {
@@ -117,25 +120,25 @@ template<> struct cbFunction::Caller<void> {
 
 };
 
-template<> struct cbFunction::Caller<double> {
+template<> struct cbCaller<double> {
 
 	template <typename... Args>
 	static double call(unsigned int num, Args... args) {
-		return(cbFunction::callDouble(num, args...));
+		return(callDouble(num, args...));
 	}
 
 };
 
-template<> struct cbFunction::Caller<float> {
+template<> struct cbCaller<float> {
 
 	template <typename... Args>
 	static float call(unsigned int num, Args... args) {
-		return(cbFunction::callDouble(num, args...));
+		return(callDouble(num, args...));
 	}
 
 };
 
-template<> struct cbFunction::Caller<cbOutput::CreateValue> {
+template<> struct cbCaller<cbOutput::CreateValue> {
 
 	template <typename... Args>
 	static int call(unsigned int num, Args... args) {
diff --git a/include/nbind/em/NBind.h b/include/nbind/em/NBind.h
index d550ad3..5aff105 100644
--- a/include/nbind/em/NBind.h
+++ b/include/nbind/em/NBind.h
@@ -29,7 +29,11 @@ class NBindID {
 };
 
 class External;
-class cbFunction;
+
+template <typename DefaultReturnType>
+class cbWrapper;
+
+typedef cbWrapper<void> cbFunction;
 
 class NBind {
 
diff --git a/include/nbind/em/StdFunction.h b/include/nbind/em/StdFunction.h
new file mode 100644
index 0000000..9ccfa63
--- /dev/null
+++ b/include/nbind/em/StdFunction.h
@@ -0,0 +1,40 @@
+// This file is part of nbind, copyright (C) 2016 BusFaster Ltd.
+// Released under the MIT license, see LICENSE.
+
+// This file handles type conversion of C++ standard library types
+// to / from JavaScript.
+
+#pragma once
+
+#include <functional>
+
+namespace nbind {
+
+#define NBIND_DEFINE_CALLBACK_TYPE(ArgType)         \
+template <typename ReturnType, typename... Args>    \
+struct BindingType<ArgType> {                       \
+                                                    \
+	typedef ArgType Type;                           \
+                                                    \
+	typedef unsigned int WireType;                  \
+                                                    \
+};                                                  \
+                                                    \
+template<typename PolicyList, typename ReturnType, typename... Args> \
+struct ArgFromWire<PolicyList, ArgType> {           \
+                                                    \
+	explicit ArgFromWire(unsigned int num) : val(cbWrapper<ReturnType>(num)) {} \
+                                                    \
+	inline ArgType get(unsigned int num) {          \
+		return(val);                                \
+	}                                               \
+                                                    \
+	std::function<ReturnType (Args...)> val;        \
+                                                    \
+}
+
+NBIND_DEFINE_CALLBACK_TYPE(std::function<ReturnType (Args...)>);
+NBIND_DEFINE_CALLBACK_TYPE(std::function<ReturnType (Args...)> &);
+NBIND_DEFINE_CALLBACK_TYPE(std::function<ReturnType (Args...)> const &);
+
+} // namespace
diff --git a/src/em/Globals.ts b/src/em/Globals.ts
index 7dad0d7..eca4563 100644
--- a/src/em/Globals.ts
+++ b/src/em/Globals.ts
@@ -8,7 +8,7 @@ import {_nbind as _type} from './BindingType';
 import {_nbind as _class} from './BindClass';
 import {_nbind as _caller} from './Caller';
 import {_nbind as _resource} from './Resource';
-import {TypeFlags, TypeSpecWithName, PolicyTbl} from '../Type';
+import {TypeFlags, TypeSpecWithName, PolicyTbl, StructureType} from '../Type';
 
 // Let decorators run eval in current scope to read function source code.
 setEvil((code: string) => eval(code));
@@ -104,16 +104,26 @@ export namespace _nbind {
 	}
 
 	export function queryType(id: number) {
-		const placeholderFlag = HEAPU8[id as number];
+		const placeholderFlag = HEAPU8[id];
+		let paramCount = structureList[placeholderFlag][1];
 
-		// TODO: get paramList length from structureList[placeholderFlag][1]
+		id /= 4;
 
-		return({
-			paramList: [
-				HEAPU32[((id as number) >> 2) + 1],
-				HEAPU32[((id as number) >> 2) + 2]
-			],
+		if(paramCount < 0) {
+			++id;
+			paramCount = HEAPU32[id] + 1;
+		}
+
+		let paramList: (number | number[])[] = Array.prototype.slice.call(
+			HEAPU32.subarray(id + 1, id + 1 + paramCount)
+		);
 
+		if(placeholderFlag == StructureType.callback) {
+			paramList = [ paramList[0], (paramList as number[]).slice(1) ];
+		}
+
+		return({
+			paramList: paramList,
 			placeholderFlag: placeholderFlag
 		});
 	}
diff --git a/src/em/em-api.ts b/src/em/em-api.ts
index 3cfdc20..168c3ed 100644
--- a/src/em/em-api.ts
+++ b/src/em/em-api.ts
@@ -108,6 +108,7 @@ class nbind { // tslint:disable-line:class-name
 			[TypeFlags.isVector]: _nbind.ArrayType,
 			[TypeFlags.isArray]: _nbind.ArrayType,
 			[TypeFlags.isCString]: _nbind.CStringType,
+			[TypeFlags.isCallback]: _nbind.CallbackType,
 			[TypeFlags.isOther]: _nbind.BindType
 		};