diff --git a/Sources/_FoundationCShims/CMakeLists.txt b/Sources/_FoundationCShims/CMakeLists.txt
index 1798a5bb0..d8e5d06a7 100644
--- a/Sources/_FoundationCShims/CMakeLists.txt
+++ b/Sources/_FoundationCShims/CMakeLists.txt
@@ -20,7 +20,7 @@ add_library(_FoundationCShims STATIC
 target_include_directories(_FoundationCShims PUBLIC include)
 
 target_compile_options(_FoundationCShims INTERFACE
-  "$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xcc -fmodule-map-file=${CMAKE_CURRENT_SOURCE_DIR}/include/module.modulemap>")
+  "$<BUILD_INTERFACE:$<$<COMPILE_LANGUAGE:Swift>:SHELL:-Xcc -fmodule-map-file=${CMAKE_CURRENT_SOURCE_DIR}/include/module.modulemap>>")
 
 set_property(GLOBAL APPEND PROPERTY SWIFT_FOUNDATION_EXPORTS _FoundationCShims)