diff --git a/src/libfetchers/fetchers.hh b/src/libfetchers/fetchers.hh
index 94b2320f9..ff04d5551 100644
--- a/src/libfetchers/fetchers.hh
+++ b/src/libfetchers/fetchers.hh
@@ -104,9 +104,9 @@ public:
 
     bool operator ==(const Input & other) const noexcept;
 
-    auto operator <=>(const Input & other) const
+    bool operator <(const Input & other) const
     {
-        return attrs <=> other.attrs;
+        return attrs < other.attrs;
     }
 
     bool contains(const Input & other) const;
diff --git a/src/libflake/flake/flakeref.hh b/src/libflake/flake/flakeref.hh
index 2ba01c72b..ec755399d 100644
--- a/src/libflake/flake/flakeref.hh
+++ b/src/libflake/flake/flakeref.hh
@@ -49,7 +49,10 @@ struct FlakeRef
 
     bool operator ==(const FlakeRef & other) const = default;
 
-    auto operator <=>(const FlakeRef &) const = default;
+    bool operator <(const FlakeRef & other) const
+    {
+        return std::tie(input, subdir) < std::tie(other.input, other.subdir);
+    }
 
     FlakeRef(fetchers::Input && input, const Path & subdir)
         : input(std::move(input)), subdir(subdir)
diff --git a/src/libutil/types.hh b/src/libutil/types.hh
index f30dd910e..9f5c75827 100644
--- a/src/libutil/types.hh
+++ b/src/libutil/types.hh
@@ -45,7 +45,10 @@ struct Explicit {
 
     bool operator ==(const Explicit<T> & other) const = default;
 
-    auto operator <=>(const Explicit<T> & other) const = default;
+    bool operator <(const Explicit<T> & other) const
+    {
+        return t < other.t;
+    }
 };