diff --git a/src/tint2conf/CMakeLists.txt b/src/tint2conf/CMakeLists.txt
index e8c6db3..134caa0 100644
--- a/src/tint2conf/CMakeLists.txt
+++ b/src/tint2conf/CMakeLists.txt
@@ -63,7 +63,7 @@ endif( NOT DATADIR )
 add_definitions( -DINSTALL_PREFIX=\"${CMAKE_INSTALL_PREFIX}\" )
 add_definitions( -DLOCALEDIR=\"${CMAKE_INSTALL_PREFIX}/${DATADIR}/locale\" )
 add_definitions( -DGETTEXT_PACKAGE=\"tint2conf\" )
-set_target_properties( tint2conf PROPERTIES COMPILE_FLAGS "-Wall -pthread" )
+set_target_properties( tint2conf PROPERTIES COMPILE_FLAGS "-Wall -pthread -std=c99" )
 set_target_properties( tint2conf PROPERTIES LINK_FLAGS "-pthread" )
 
 add_subdirectory(po)