diff --git a/jerry-core/ecma/base/ecma-magic-strings.inc.h b/jerry-core/ecma/base/ecma-magic-strings.inc.h
index 81f31ac2ce..54918843a9 100644
--- a/jerry-core/ecma/base/ecma-magic-strings.inc.h
+++ b/jerry-core/ecma/base/ecma-magic-strings.inc.h
@@ -213,3 +213,4 @@ ECMA_MAGIC_STRING_DEF (ECMA_MAGIC_STRING__EMPTY, "")
  * Implementation-defined magic strings
  */
 ECMA_MAGIC_STRING_DEF (ECMA_MAGIC_STRING_JERRY_UL, "Jerry")
+ECMA_MAGIC_STRING_DEF (ECMA_MAGIC_STRING__FUNCTION_TO_STRING, "function(){/* ecmascript */}")
diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-function-prototype.cpp b/jerry-core/ecma/builtin-objects/ecma-builtin-function-prototype.cpp
index deb43be95c..3cadb23a27 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-function-prototype.cpp
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-function-prototype.cpp
@@ -55,7 +55,18 @@
 static ecma_completion_value_t
 ecma_builtin_function_prototype_object_to_string (ecma_value_t this_arg) /**< this argument */
 {
-  ECMA_BUILTIN_CP_UNIMPLEMENTED (this_arg);
+  ecma_completion_value_t ret_value = ecma_make_empty_completion_value ();
+
+  if (!ecma_op_is_callable (this_arg))
+  {
+    ret_value = ecma_make_throw_obj_completion_value (ecma_new_standard_error (ECMA_ERROR_TYPE));
+  }
+  else
+  {
+    ecma_string_t *function_to_string_p = ecma_get_magic_string (ECMA_MAGIC_STRING__FUNCTION_TO_STRING);
+    ret_value = ecma_make_normal_completion_value (ecma_make_string_value (function_to_string_p));
+  }
+  return ret_value;
 } /* ecma_builtin_function_prototype_object_to_string */
 
 /**
diff --git a/tests/jerry/function_prototype_tostring.js b/tests/jerry/function_prototype_tostring.js
new file mode 100644
index 0000000000..6c6e219c59
--- /dev/null
+++ b/tests/jerry/function_prototype_tostring.js
@@ -0,0 +1,28 @@
+// Copyright 2015 Samsung Electronics Co., Ltd.
+// Copyright 2015 University of Szeged
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+assert (Math.cos.toString() === "function(){/* ecmascript */}");
+
+function none() { return 1; }
+assert (none.toString() === "function(){/* ecmascript */}");
+
+function single(b) { return 1; }
+assert (single.toString() === "function(){/* ecmascript */}");
+
+function multiple(a,b) { return 1; }
+assert (multiple.toString() === "function(){/* ecmascript */}");
+
+function lots(a,b,c,d,e,f,g,h,i,j,k) { return 1; }
+assert (lots.toString() === "function(){/* ecmascript */}");