diff --git a/.gitignore b/.gitignore
index a8f12de9..7e623b17 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,3 +33,7 @@ _ReSharper*/
 *.suo
 *.sdf
 lib/
+*.ninja*
+CMakeCache.txt
+CMakeFiles/
+cmake_install.cmake
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2c82d2b1..b11bc933 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -65,7 +65,11 @@ if(WIN32)
 	if(MINGW)
 		add_definitions(-DNANA_MINGW)
 		add_definitions(-DSTD_CODECVT_NOT_SUPPORTED)
-		option(NANA_THREAD_NOT_SUPPORTED "Use this flag if MinGW version is older than 4.8.1" ON)
+		if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
+			if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.8.1")
+				option(NANA_THREAD_NOT_SUPPORTED "Use this flag if MinGW version is older than 4.8.1" ON)
+			endif()
+		endif()
 		if(NANA_THREAD_NOT_SUPPORTED)
 			add_definitions(-DSTD_THREAD_NOT_SUPPORTED)
 		endif()
diff --git a/source/filesystem/filesystem.cpp b/source/filesystem/filesystem.cpp
index 80396b00..50e28e33 100644
--- a/source/filesystem/filesystem.cpp
+++ b/source/filesystem/filesystem.cpp
@@ -430,8 +430,7 @@ namespace nana {
 						delete[] p;
 						return s;
 					}
-					nana::string s = buf;
-					return s;
+					return nana::string(buf);
 				}
 #elif defined(NANA_LINUX)
 				const char * s = ::getenv("PWD");