diff --git a/meson.build b/meson.build
index e90bf213b..5885905c5 100644
--- a/meson.build
+++ b/meson.build
@@ -406,6 +406,7 @@ add_project_arguments(
   '-Werror=switch',
   '-Werror=switch-enum',
   '-Wdeprecated-copy',
+  '-Wignored-qualifiers',
   # Enable assertions in libstdc++ by default. Harmless on libc++. Benchmarked
   # at ~1% overhead in `nix search`.
   #
diff --git a/src/libfetchers/tarball.cc b/src/libfetchers/tarball.cc
index 68cb0ca40..cda6b7acb 100644
--- a/src/libfetchers/tarball.cc
+++ b/src/libfetchers/tarball.cc
@@ -186,7 +186,7 @@ struct CurlInputScheme : InputScheme
     virtual const std::string inputType() const = 0;
     const std::set<std::string> transportUrlSchemes = {"file", "http", "https"};
 
-    const bool hasTarballExtension(std::string_view path) const
+    bool hasTarballExtension(std::string_view path) const
     {
         return path.ends_with(".zip") || path.ends_with(".tar")
             || path.ends_with(".tgz") || path.ends_with(".tar.gz")