diff --git a/src/catch2/internal/catch_istream.cpp b/src/catch2/internal/catch_istream.cpp
index 4cd35058..6d1fa94b 100644
--- a/src/catch2/internal/catch_istream.cpp
+++ b/src/catch2/internal/catch_istream.cpp
@@ -78,6 +78,7 @@ namespace Detail {
             FileStream( std::string const& filename ) {
                 m_ofs.open( filename.c_str() );
                 CATCH_ENFORCE( !m_ofs.fail(), "Unable to open file: '" << filename << '\'' );
+                m_ofs << std::unitbuf;
             }
             ~FileStream() override = default;
         public: // IStream