diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3012be94984..ddbb5447b3d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,8 +30,6 @@ set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 set(CMAKE_MSVC_RUNTIME_LIBRARY MultiThreadedDLL)
 set(CMAKE_POSITION_INDEPENDENT_CODE ${BUILD_SHARED_LIBS})
 
-add_compile_options(-DUSE_IMPL_ONLY_IMPORTS)
-
 if(FIND_PM_DEPS)
   find_package(SwiftSystem CONFIG REQUIRED)
   find_package(TSC CONFIG REQUIRED)
diff --git a/Sources/CMakeLists.txt b/Sources/CMakeLists.txt
index 07863f734cf..70b07e10d3d 100644
--- a/Sources/CMakeLists.txt
+++ b/Sources/CMakeLists.txt
@@ -6,6 +6,8 @@
 # See http://swift.org/LICENSE.txt for license information
 # See http://swift.org/CONTRIBUTORS.txt for Swift project authors
 
+add_compile_definitions(USE_IMPL_ONLY_IMPORTS)
+
 add_subdirectory(SPMSQLite3)
 add_subdirectory(Basics)
 add_subdirectory(Build)