diff --git a/src/libutil/args.cc b/src/libutil/args.cc
index 2e6d85afd..f4309473b 100644
--- a/src/libutil/args.cc
+++ b/src/libutil/args.cc
@@ -81,6 +81,8 @@ std::optional<std::string> RootArgs::needsCompletion(std::string_view s)
     return {};
 }
 
+namespace {
+
 /**
  * Basically this is `typedef std::optional<Parser> Parser(std::string_view s, Strings & r);`
  *
@@ -246,6 +248,8 @@ void ParseQuoted::operator()(std::shared_ptr<Parser> & state, Strings & r)
     assert(false);
 }
 
+} // namespace
+
 Strings parseShebangContent(std::string_view s)
 {
     Strings result;
diff --git a/src/nix/diff-closures.cc b/src/nix/diff-closures.cc
index 020c3e13b..cbf842e5c 100644
--- a/src/nix/diff-closures.cc
+++ b/src/nix/diff-closures.cc
@@ -10,11 +10,15 @@
 
 namespace nix {
 
+namespace {
+
 struct Info
 {
     std::string outputName;
 };
 
+} // namespace
+
 // name -> version -> store paths
 typedef std::map<std::string, std::map<std::string, std::map<StorePath, Info>>> GroupedPaths;