diff --git a/CMakeLists.txt b/CMakeLists.txt
index aec964da9..86439ada4 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,7 +19,7 @@ if(CMAKE_COMPILER_IS_CLANG)
   set(CMAKE_C_FLAGS_DEBUG "-g3 -O0")
   set(CMAKE_C_FLAGS_COVERAGE "-g3 -O0 --coverage")
   set(CMAKE_C_FLAGS_ASAN "-fsanitize=address -fno-omit-frame-pointer -g3 -O1")
-  set(CMAKE_C_FLAGS_CHECK "${CMAKE_C_FLAGS} -Werror -O1 -Wpointer-arith -Wwrite-strings -Wdocumentation -Wunreachable-code -Wmissing-prototypes")
+  set(CMAKE_C_FLAGS_CHECK "${CMAKE_C_FLAGS} -Werror -O1 -Wpointer-arith -Wwrite-strings -Wdocumentation -Wunreachable-code")
 endif(CMAKE_COMPILER_IS_CLANG)
 
 set(CMAKE_BUILD_TYPE ${CMAKE_BUILD_TYPE}
diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index 2e202de78..c57e14f2b 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -82,6 +82,10 @@ if(CMAKE_COMPILER_IS_GNUCC)
   set(CMAKE_C_FLAGS_CHECKFULL "${CMAKE_C_FLAGS_CHECK} -Wcast-qual")
 endif(CMAKE_COMPILER_IS_GNUCC)
 
+if(CMAKE_COMPILER_IS_CLANG)
+  set(CMAKE_C_FLAGS_CHECK "${CMAKE_C_FLAGS_CHECK} -Wmissing-declarations -Wmissing-prototypes")
+endif(CMAKE_COMPILER_IS_CLANG)
+
 if (NOT USE_STATIC_POLARSSL_LIBRARY AND NOT USE_SHARED_POLARSSL_LIBRARY)
 	message(FATAL_ERROR "Need to choose static or shared polarssl build!")
 endif(NOT USE_STATIC_POLARSSL_LIBRARY AND NOT USE_SHARED_POLARSSL_LIBRARY)