diff --git a/coding/file_container.cpp b/coding/file_container.cpp
index 082ebda4c8..21524a7538 100644
--- a/coding/file_container.cpp
+++ b/coding/file_container.cpp
@@ -169,7 +169,7 @@ MappedFile::Handle MappedFile::Map(uint64_t offset, uint64_t size, string const
 #else
   void * pMap = mmap(0, length, PROT_READ, MAP_SHARED, m_fd, alignedOffset);
   if (pMap == MAP_FAILED)
-    MYTHROW(Reader::OpenException, ("Can't map section:", tag, "with [offset, size]:", offset, size));
+    MYTHROW(Reader::OpenException, ("Can't map section:", tag, "with [offset, size]:", offset, size, "errno:", errno));
 #endif
 
   char const * data = reinterpret_cast<char const *>(pMap);