diff --git a/tools/SourceKit/tools/swift-lang/CMakeLists.txt b/tools/SourceKit/tools/swift-lang/CMakeLists.txt
index 2357745f8dbb..5a929de37e0d 100644
--- a/tools/SourceKit/tools/swift-lang/CMakeLists.txt
+++ b/tools/SourceKit/tools/swift-lang/CMakeLists.txt
@@ -1,4 +1,4 @@
-if(NOT SWIFT_SOURCEKIT_USE_INPROC_LIBRARY AND SWIFT_BUILD_STDLIB)
+if(NOT SWIFT_SOURCEKIT_USE_INPROC_LIBRARY AND SWIFT_BUILD_STDLIB AND SWIFT_BUILD_SDK_OVERLAY)
   set(EXTRA_COMPILE_FLAGS "-F" "${SWIFT_LIBRARY_OUTPUT_INTDIR}")
   set(SOURCEKITD_LINK_LIBS sourcekitd)
   set(INSTALLED_COMP sourcekit-xpc-service)