diff --git a/src/libexpr/flake/lockfile.cc b/src/libexpr/flake/lockfile.cc
index a74e68c9c..ba2fd46f0 100644
--- a/src/libexpr/flake/lockfile.cc
+++ b/src/libexpr/flake/lockfile.cc
@@ -234,6 +234,11 @@ bool LockFile::operator ==(const LockFile & other) const
     return toJSON() == other.toJSON();
 }
 
+bool LockFile::operator !=(const LockFile & other) const
+{
+    return !(*this == other);
+}
+
 InputPath parseInputPath(std::string_view s)
 {
     InputPath path;
diff --git a/src/libexpr/flake/lockfile.hh b/src/libexpr/flake/lockfile.hh
index 6512509c5..4616a77f6 100644
--- a/src/libexpr/flake/lockfile.hh
+++ b/src/libexpr/flake/lockfile.hh
@@ -67,6 +67,9 @@ struct LockFile
     std::optional<FlakeRef> isUnlocked() const;
 
     bool operator ==(const LockFile & other) const;
+    // Needed for old gcc versions that don't syntethise it (like gcc 8.2.2
+    // that is still the default on aarch64-linux)
+    bool operator !=(const LockFile & other) const;
 
     std::shared_ptr<Node> findInput(const InputPath & path);