diff --git a/core_service.go b/core_service.go
index a6c124e..9737ce9 100644
--- a/core_service.go
+++ b/core_service.go
@@ -126,7 +126,7 @@ func (s *CoreService) handleMissingKey(mk MissingKey) {
 	}
 	s.missingKeysMu.Lock()
 	defer s.missingKeysMu.Unlock()
-	s.missingKeys = append(s.missingKeys, mk)
+	s.missingKeys = append(s.missingKeys, cloneMissingKey(mk))
 }
 
 // MissingKeys returns all missing keys collected in collect mode.
@@ -137,7 +137,9 @@ func (s *CoreService) MissingKeys() []MissingKey {
 	s.missingKeysMu.Lock()
 	defer s.missingKeysMu.Unlock()
 	result := make([]MissingKey, len(s.missingKeys))
-	copy(result, s.missingKeys)
+	for i, mk := range s.missingKeys {
+		result[i] = cloneMissingKey(mk)
+	}
 	return result
 }
 
diff --git a/core_service_test.go b/core_service_test.go
index a14c95e..23ad650 100644
--- a/core_service_test.go
+++ b/core_service_test.go
@@ -49,3 +49,22 @@ func TestCoreServiceNilSafe(t *testing.T) {
 	require.ErrorIs(t, svc.AddLoader(nil), ErrServiceNotInitialised)
 	require.ErrorIs(t, svc.LoadFS(nil, "locales"), ErrServiceNotInitialised)
 }
+
+func TestCoreServiceMissingKeysReturnsCopies(t *testing.T) {
+	svc, err := New()
+	require.NoError(t, err)
+	coreSvc := &CoreService{svc: svc}
+
+	coreSvc.SetMode(ModeCollect)
+	_ = svc.T("missing.copy.key", map[string]any{"foo": "bar"})
+
+	missing := coreSvc.MissingKeys()
+	require.Len(t, missing, 1)
+	require.Equal(t, "bar", missing[0].Args["foo"])
+
+	missing[0].Args["foo"] = "mutated"
+
+	again := coreSvc.MissingKeys()
+	require.Len(t, again, 1)
+	assert.Equal(t, "bar", again[0].Args["foo"])
+}
diff --git a/hooks.go b/hooks.go
index 7a8b0f4..32b7467 100644
--- a/hooks.go
+++ b/hooks.go
@@ -201,7 +201,7 @@ func dispatchMissingKey(key string, args map[string]any) {
 		return
 	}
 	file, line := missingKeyCaller()
-	mk := MissingKey{Key: key, Args: args, CallerFile: file, CallerLine: line}
+	mk := cloneMissingKey(MissingKey{Key: key, Args: args, CallerFile: file, CallerLine: line})
 	for _, h := range state.handlers {
 		if h != nil {
 			h(mk)
@@ -209,6 +209,19 @@ func dispatchMissingKey(key string, args map[string]any) {
 	}
 }
 
+func cloneMissingKey(mk MissingKey) MissingKey {
+	if len(mk.Args) == 0 {
+		mk.Args = nil
+		return mk
+	}
+	args := make(map[string]any, len(mk.Args))
+	for key, value := range mk.Args {
+		args[key] = value
+	}
+	mk.Args = args
+	return mk
+}
+
 func missingKeyCaller() (string, int) {
 	const packagePrefix = "dappco.re/go/core/i18n."