diff --git a/rdtk/CMakeLists.txt b/rdtk/CMakeLists.txt
index 5ccd47320..f219eb2fb 100644
--- a/rdtk/CMakeLists.txt
+++ b/rdtk/CMakeLists.txt
@@ -72,9 +72,7 @@ include(GNUInstallDirsWrapper)
 include(CMakePackageConfigHelpers)
 include (SetFreeRDPCMakeInstallDir)
 
-if(BUILD_SHARED_LIBS)
-    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DRDTK_EXPORTS")
-endif()
+add_definitions(-DRDTK_EXPORTS)
 
 if (NOT IOS)
 	check_include_files(stdbool.h WINPR_HAVE_STDBOOL_H)
diff --git a/winpr/CMakeLists.txt b/winpr/CMakeLists.txt
index 7ab46df25..51d667f71 100644
--- a/winpr/CMakeLists.txt
+++ b/winpr/CMakeLists.txt
@@ -278,7 +278,7 @@ if(BUILD_SHARED_LIBS)
 	set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DWINPR_DLL")
 endif()
 
-set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DWINPR_EXPORTS")
+add_definitions(-DWINPR_EXPORTS)
 
 # Enable 64bit file support on linux and FreeBSD.
 if("${CMAKE_SYSTEM_NAME}" MATCHES "Linux" OR FREEBSD)