diff --git a/CMakeLists.txt b/CMakeLists.txt
index 31f73cf..f5c40d5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -83,6 +83,14 @@ if ( MSVC )
     set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /W4 ")
 endif( MSVC )
 
+if (CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  # using regular Clang or AppleClang
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall")
+elseif ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "GNU")
+  # using GCC
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall")
+endif()
+
 IF(JSONCPP_WITH_WARNING_AS_ERROR)
     UseCompilationWarningAsError()
 ENDIF(JSONCPP_WITH_WARNING_AS_ERROR)