diff --git a/.travis.yml b/.travis.yml
index 10b6f54a..5bd9b6eb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -5,11 +5,11 @@
 sudo: required
 language: cpp
 
-# gcc 4.8
-addons: &gcc48
+# gcc 4.9
+addons: &gcc49
   apt:
     packages:
-      - g++-4.8
+      - g++-4.9
     sources:
       - ubuntu-toolchain-r-test
 
@@ -44,39 +44,35 @@ addons: &clang10
 
 matrix:
   include:
-    # Test gcc-4.8: C++11, Build=Debug/Release
-    - env: GCC_VERSION=4.8 BUILD_TYPE=Debug CPP=11
+    # Test gcc-4.9: C++14, Build=Debug/Release
+    - env: GCC_VERSION=4.9 BUILD_TYPE=Debug CPP=14
       os: linux
-      addons: *gcc48
+      addons: *gcc49
 
-    - env: GCC_VERSION=4.8 BUILD_TYPE=Release CPP=11
+    - env: GCC_VERSION=4.9 BUILD_TYPE=Release CPP=14
       os: linux
-      addons: *gcc48
+      addons: *gcc49
 
-    - env: GCC_VERSION=7 BUILD_TYPE=Release CPP=11
+    - env: GCC_VERSION=7 BUILD_TYPE=Release CPP=14
       os: linux
       addons: *gcc7
 
-    # Test clang-3.5: C++11, Build=Debug/Release
-    - env: CLANG_VERSION=3.5 BUILD_TYPE=Debug CPP=11
-      os: linux
-      addons: *clang35
-
-    - env: CLANG_VERSION=3.5 BUILD_TYPE=Release CPP=11
+    # Test clang-3.5: C++11, Build=Release
+    - env: CLANG_VERSION=3.5 BUILD_TYPE=Release CPP=14
       os: linux
       addons: *clang35
 
       # osx
-    - env: BUILD_TYPE=Release CPP=11 ASAN=Off TSAN=Off
+    - env: BUILD_TYPE=Release CPP=14 ASAN=Off TSAN=Off
       os: osx
 
     # Test clang-10.0: C++11, Build=Debug/Release
-    - env: CLANG_VERSION=10 BUILD_TYPE=Debug CPP=11
+    - env: CLANG_VERSION=10 BUILD_TYPE=Debug CPP=14
       os: linux
       dist: bionic
       addons: *clang10
 
-    - env: CLANG_VERSION=10 BUILD_TYPE=Release CPP=11 ASAN=On
+    - env: CLANG_VERSION=10 BUILD_TYPE=Release CPP=14 ASAN=On
       os: linux
       dist: bionic
       addons: *clang10
@@ -100,11 +96,9 @@ script:
       -DCMAKE_BUILD_TYPE=$BUILD_TYPE \
       -DCMAKE_CXX_STANDARD=$CPP \
       -DSPDLOG_BUILD_EXAMPLE=ON \
-      -DSPDLOG_BUILD_EXAMPLE_HO=ON \
       -DSPDLOG_BUILD_WARNINGS=ON \
       -DSPDLOG_BUILD_BENCH=OFF \
       -DSPDLOG_BUILD_TESTS=ON \
-      -DSPDLOG_BUILD_TESTS_HO=OFF \
       -DSPDLOG_SANITIZE_ADDRESS=$ASAN 
       
   - make VERBOSE=1 -j2
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1327315b..fe81fa60 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -159,7 +159,7 @@ if (SPDLOG_BUILD_SHARED)
     add_library(spdlog SHARED ${SPDLOG_SRCS} ${SPDLOG_ALL_HEADERS})
     target_compile_definitions(spdlog PUBLIC SPDLOG_SHARED_LIB)
     if (WIN32)
-        target_compile_options(spdlog PUBLIC /wd4251 /wd4275)
+        target_compile_options(spdlog PUBLIC /wd4251 /wd4275 /wd4661)
         configure_file(${CMAKE_CURRENT_SOURCE_DIR}/cmake/version.rc.in ${CMAKE_CURRENT_BINARY_DIR}/version.rc @ONLY)
     endif ()
     if (NOT SPDLOG_FMT_EXTERNAL AND NOT SPDLOG_FMT_EXTERNAL_HO)
diff --git a/README.md b/README.md
index c3081c77..f4a3db78 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # spdlog
 
-Very fast, header-only/compiled, C++ logging library. [![Build Status](https://travis-ci.org/gabime/spdlog.svg?branch=v1.x)](https://travis-ci.org/gabime/spdlog)  [![Build status](https://ci.appveyor.com/api/projects/status/d2jnxclg20vd0o50?svg=true)](https://ci.appveyor.com/project/gabime/spdlog) [![Release](https://img.shields.io/github/release/gabime/spdlog.svg)](https://github.com/gabime/spdlog/releases/latest)
+Very fast, header-only/compiled, C++ logging library. [![Build Status](https://travis-ci.org/gabime/spdlog.svg?branch=v2.x)](https://travis-ci.org/gabime/spdlog)  [![Build status](https://ci.appveyor.com/api/projects/status/d2jnxclg20vd0o50?svg=true)](https://ci.appveyor.com/project/gabime/spdlog) [![Release](https://img.shields.io/github/release/gabime/spdlog.svg)](https://github.com/gabime/spdlog/releases/latest)
 
 ## Install 
 #### Header only version
diff --git a/appveyor.yml b/appveyor.yml
index 3b654760..a7283bb1 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -40,7 +40,7 @@ build_script:
 
       set PATH=%PATH%;C:\Program Files\Git\usr\bin
 
-      cmake .. -G %GENERATOR% -DCMAKE_BUILD_TYPE=%BUILD_TYPE% -DSPDLOG_WCHAR_SUPPORT=%WCHAR% -DSPDLOG_BUILD_SHARED=%BUILD_SHARED% -DSPDLOG_BUILD_EXAMPLE=ON -DSPDLOG_BUILD_EXAMPLE_HO=ON -DSPDLOG_BUILD_TESTS=ON -DSPDLOG_BUILD_TESTS_HO=OFF -DSPDLOG_BUILD_WARNINGS=ON
+      cmake .. -G %GENERATOR% -DCMAKE_BUILD_TYPE=%BUILD_TYPE% -DSPDLOG_WCHAR_SUPPORT=%WCHAR% -DSPDLOG_BUILD_SHARED=%BUILD_SHARED% -DSPDLOG_BUILD_EXAMPLE=ON  -DSPDLOG_BUILD_TESTS=ON -DSPDLOG_BUILD_WARNINGS=ON
 
       cmake --build . --config %BUILD_TYPE%
 
diff --git a/include/spdlog/fmt/fmt.h b/include/spdlog/fmt/fmt.h
index f05495ef..ca5669fc 100644
--- a/include/spdlog/fmt/fmt.h
+++ b/include/spdlog/fmt/fmt.h
@@ -11,9 +11,6 @@
 //
 
 #if !defined(SPDLOG_FMT_EXTERNAL)
-#if !defined(FMT_HEADER_ONLY)
-#define FMT_HEADER_ONLY
-#endif
 #ifndef FMT_USE_WINDOWS_H
 #define FMT_USE_WINDOWS_H 0
 #endif
diff --git a/src/sinks/basic_file_sink.cpp b/src/sinks/basic_file_sink.cpp
index 0b570053..ead8ae00 100644
--- a/src/sinks/basic_file_sink.cpp
+++ b/src/sinks/basic_file_sink.cpp
@@ -4,6 +4,8 @@
 #include <spdlog/sinks/basic_file_sink.h>
 #include <spdlog/common.h>
 #include <spdlog/details/os.h>
+#include <spdlog/details/null_mutex.h>
+#include <mutex>
 
 namespace spdlog {
 namespace sinks {
diff --git a/src/sinks/stdout_color_sinks.cpp b/src/sinks/stdout_color_sinks.cpp
index 9c63e834..2165db2e 100644
--- a/src/sinks/stdout_color_sinks.cpp
+++ b/src/sinks/stdout_color_sinks.cpp
@@ -33,6 +33,8 @@ std::shared_ptr<logger> stderr_color_st(const std::string &logger_name, color_mo
     return Factory::template create<sinks::stderr_color_sink_st>(logger_name, mode);
 }
 
+} // namespace spdlog
+
 // template instantiations
 template SPDLOG_API std::shared_ptr<spdlog::logger> spdlog::stdout_color_mt<spdlog::synchronous_factory>(
     const std::string &logger_name, color_mode mode);
@@ -51,5 +53,3 @@ template SPDLOG_API std::shared_ptr<spdlog::logger> spdlog::stderr_color_mt<spdl
     const std::string &logger_name, color_mode mode);
 template SPDLOG_API std::shared_ptr<spdlog::logger> spdlog::stderr_color_st<spdlog::async_factory>(
     const std::string &logger_name, color_mode mode);
-
-} // namespace spdlog
\ No newline at end of file