diff --git a/lib/Support/Windows/PathV2.inc b/lib/Support/Windows/PathV2.inc
index c79d8ab0aa6..66eeab058f6 100644
--- a/lib/Support/Windows/PathV2.inc
+++ b/lib/Support/Windows/PathV2.inc
@@ -793,10 +793,12 @@ error_code detail::directory_iterator_increment(detail::DirIterState &it) {
 error_code map_file_pages(const Twine &path, off_t file_offset, size_t size,  
                                             bool map_writable, void *&result) {
   assert(0 && "NOT IMPLEMENTED");
+  return windows_error::invalid_function;
 }
 
 error_code unmap_file_pages(void *base, size_t size) {
   assert(0 && "NOT IMPLEMENTED");
+  return windows_error::invalid_function;
 }