diff --git a/doc/how_to_build_macosx.md b/doc/how_to_build_macosx.md
index 68532df..aebfa5e 100644
--- a/doc/how_to_build_macosx.md
+++ b/doc/how_to_build_macosx.md
@@ -12,7 +12,7 @@
   - http://download.qt.io/official_releases/qt/5.5/5.5.1/
     - qt-opensource-mac-x64-clang-5.5.1.dmg
 - boost
-  - http://www.boost.org/users/history/version_1_55_0.html
+  - http://www.boost.org/users/history/version_1_55_0.html (or later, though only 1.55.0 is supported)
 
 ## Building on MacOSX
 
diff --git a/doc/how_to_build_win.md b/doc/how_to_build_win.md
index 5b050fa..7c62b9c 100644
--- a/doc/how_to_build_win.md
+++ b/doc/how_to_build_win.md
@@ -33,11 +33,13 @@ They will have to be installed seperately as follows.
   - qt-opensource-windows-x86-msvc2013_64-5.5.1.exe
 
 ### boost
+- boost 1.55.0 or later is required (tested up to 1.60.0), but the support build is using 1.55.0 exactly.
 - http://www.boost.org/users/history/version_1_55_0.html
 - Download boost_1_55_0.zip from the above link.  Extract all contents to the '$opentoonz/thirdparty/boost' directory.
 - Install the following path for Visual Studio 2013
   - https://svn.boost.org/trac/boost/attachment/ticket/9369/vc12_fix_has_member_function_callable_with.patch
 
+
 ## Building
 
 ### Using CMake to Create a Visual Studio Project
diff --git a/toonz/sources/CMakeLists.txt b/toonz/sources/CMakeLists.txt
index a6a373d..f31e455 100644
--- a/toonz/sources/CMakeLists.txt
+++ b/toonz/sources/CMakeLists.txt
@@ -187,8 +187,10 @@ endif()
 
 include_directories(BEFORE ${TIFF_INCLUDE_DIR} ${PNG_INCLUDE_DIRS})
 
-find_path(BOOST_ROOT include/boost boost HINTS ${THIRDPARTY_LIBS_HINTS} PATH_SUFFIXES boost155/1.55.0_1 boost/boost_1_55_0/)
-find_package(Boost 1.55 EXACT REQUIRED)
+find_path(BOOST_ROOT include/boost boost HINTS ${THIRDPARTY_LIBS_HINTS}
+	PATH_SUFFIXES boost/boost_1_60_0/ boost/boost_1_59_0/
+	boost/boost_1_58_0/ boost/boost_1_57_0/ boost/boost_1_56_0/ boost155/1.55.0_1/ boost/boost_1_55_0/ )
+find_package(Boost 1.55 REQUIRED)
 
 include_directories(${Boost_INCLUDE_DIR} ${LZ4_LIB_INCLUDE_DIRS} ${USB_LIB_INCLUDE_DIRS} ${SUPERLU_INCLUDE_DIR} ${JPEG_INCLUDE_DIR})
 
diff --git a/toonz/sources/tnztools/filltool.cpp b/toonz/sources/tnztools/filltool.cpp
index 60e82d5..7b58b64 100644
--- a/toonz/sources/tnztools/filltool.cpp
+++ b/toonz/sources/tnztools/filltool.cpp
@@ -1722,7 +1722,7 @@ public:
 		/*--- 線分上にある全ての点でdoFillを行う ---*/
 		double dx = m_mousePosition.x - m_startPosition.x;
 		double dy = m_mousePosition.y - m_startPosition.y;
-		if (abs(dx) > abs(dy)) /*-- 横長の線分の場合 --*/
+		if (std::abs(dx) > std::abs(dy)) /*-- 横長の線分の場合 --*/
 		{
 			double k = dy / dx; /*-- 直線の傾き --*/
 			/*--- roundでは負値のときにうまく繋がらない ---*/