diff --git a/CMakeLists.txt b/CMakeLists.txt
index de525e2c4..ac1c3a6e4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -57,7 +57,7 @@ elseif(CMAKE_COMPILER_IS_GNUCXX OR "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
 endif()
 
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -pedantic -Werror")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -pedantic -Werror -Wextra")
 
 if(FLATBUFFERS_CODE_COVERAGE)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g -fprofile-arcs -ftest-coverage")
diff --git a/include/flatbuffers/flatbuffers.h b/include/flatbuffers/flatbuffers.h
index 0a0ef173a..d5f53bf7b 100644
--- a/include/flatbuffers/flatbuffers.h
+++ b/include/flatbuffers/flatbuffers.h
@@ -613,7 +613,7 @@ class FlatBufferBuilder {
     return CreateVectorOfStructs(v.data(), v.size());
   }
 
-  static const int kFileIdentifierLength = 4;
+  static const size_t kFileIdentifierLength = 4;
 
   // Finish serializing a buffer by writing the root offset.
   // If a file_identifier is given, the buffer will be prefix with a standard