diff --git a/Modules/ExternalProject.cmake b/Modules/ExternalProject.cmake
index 0302d5c4b..5f5dec014 100644
--- a/Modules/ExternalProject.cmake
+++ b/Modules/ExternalProject.cmake
@@ -713,6 +713,8 @@ function(_ep_add_download_command name)
       _ep_write_extractfile_script("${stamp_dir}/extract-${name}.cmake" "${file}" "${tmp_dir}" "${source_dir}")
       list(APPEND cmd ${CMAKE_COMMAND} -P ${stamp_dir}/extract-${name}.cmake)
     endif()
+  elseif(source_dir AND EXISTS "${source_dir}")
+    set(cmd echo Sources present at ${source_dir})
   else()
     message(SEND_ERROR "error: no download info for '${name}' -- please specify existing SOURCE_DIR or one of URL, CVS_REPOSITORY and CVS_MODULE, SVN_REPOSITORY or DOWNLOAD_COMMAND")
   endif()