diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9b67ab02c..e7c9f4b89 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -27,8 +27,8 @@ project(weechat C)
 set(CMAKE_VERBOSE_MAKEFILE OFF)
 set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/cmake ${CMAKE_MODULE_PATH})
 set(CMAKE_SKIP_RPATH ON)
-set(CMAKE_C_FLAGS   "${CMAKE_C_FLAGS} -fsigned-char -fms-extensions -Wall -Wextra -Werror-implicit-function-declaration")
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsigned-char -fms-extensions -Wall -Wextra")
+set(CMAKE_C_FLAGS   "${CMAKE_C_FLAGS} -fsigned-char -fms-extensions -Wall -Wextra -Werror-implicit-function-declaration -Wformat-overflow=2 -Wformat-truncation=2")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsigned-char -fms-extensions -Wall -Wextra -Wformat-overflow=2 -Wformat-truncation=2")
 
 # version
 execute_process(COMMAND ${CMAKE_SOURCE_DIR}/version.sh devel-major OUTPUT_VARIABLE VERSION_MAJOR)