diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 7591a9f25..753846329 100755
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -3,9 +3,6 @@ project (eressea C)
 
 IF(CMAKE_COMPILER_IS_GNUCC)
     SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -pedantic -Wall -Werror -Wno-unknown-pragmas -Wstrict-prototypes -Wpointer-arith -Wno-char-subscripts -Wno-long-long")
-    SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c99 -DHAVE__BOOL")
-ELSE(CMAKE_COMPILER_IS_GNUCC)
-    MESSAGE(STATUS "Unknown compiler ${CMAKE_C_COMPILER_ID}")
 ENDIF(CMAKE_COMPILER_IS_GNUCC)
 
 set (ERESSEA_LIBRARY ${PROJECT_NAME} CACHE INTERNAL "Eressea Core Library")