diff --git a/src/source.cpp b/src/source.cpp
index 901b4f9..0d03bf9 100644
--- a/src/source.cpp
+++ b/src/source.cpp
@@ -57,8 +57,13 @@ Glib::RefPtr<Gsv::Language> Source::guess_language(const boost::filesystem::path
   if(result_uncertain)
     content_type.clear();
   auto language = language_manager->guess_language(filename, content_type);
+  auto extension = file_path.extension().string();
+  if(!language && (extension == ".in" || extension == ".bak")) {
+    auto path_copy = file_path;
+    path_copy.replace_extension();
+    return guess_language(path_copy);
+  }
   if(!language) {
-    auto extension = file_path.extension().string();
     if(filename == "CMakeLists.txt")
       language = language_manager->get_language("cmake");
     else if(filename == "meson.build")
@@ -90,7 +95,7 @@ Glib::RefPtr<Gsv::Language> Source::guess_language(const boost::filesystem::path
     }
   }
   else if(language->get_id() == "cuda") {
-    if(file_path.extension() == ".cuh")
+    if(extension == ".cuh")
       language = language_manager->get_language("cpphdr");
     else
       language = language_manager->get_language("cpp");