diff --git a/include/CMakeLists.txt b/include/CMakeLists.txt
index deed1a110..b1d6acb2b 100644
--- a/include/CMakeLists.txt
+++ b/include/CMakeLists.txt
@@ -10,7 +10,7 @@ set(LIBCXX_HEADER_PATTERN
   ${LIBCXX_SUPPORT_HEADER_PATTERN}
   )
 
-if(NOT LIBCXX_USING_INSTALLED_LLVM)
+if(NOT LIBCXX_USING_INSTALLED_LLVM AND LLVM_BINARY_DIR)
   file(COPY .
     DESTINATION "${LLVM_BINARY_DIR}/include/c++/v1"
     FILES_MATCHING