diff --git a/src/build.c b/src/build.c
index 90db3c7a..07e18ea4 100644
--- a/src/build.c
+++ b/src/build.c
@@ -338,6 +338,8 @@ static GeanyBuildCommand *get_next_build_cmd(GeanyDocument *doc, guint cmdgrp, g
 	GeanyFiletype *ft = NULL;
 	guint sink, *fr = &sink;
 
+	g_return_val_if_fail(doc == NULL || doc->is_valid, NULL);
+
 	if (printbuildcmds)
 		printfcmds();
 	if (cmdgrp >= GEANY_GBG_COUNT)
@@ -716,6 +718,8 @@ static gchar *build_replace_placeholder(const GeanyDocument *doc, const gchar *s
 	gchar *executable = NULL;
 	gchar *ret_str; /* to be freed when not in use anymore */
 
+	g_return_val_if_fail(doc == NULL || doc->is_valid, NULL);
+
 	stack = g_string_new(src);
 	if (doc != NULL && doc->file_name != NULL)
 	{
@@ -780,6 +784,8 @@ static GPid build_spawn_cmd(GeanyDocument *doc, const gchar *cmd, const gchar *d
 	gint stderr_fd;
 #endif
 
+	g_return_val_if_fail(doc == NULL || doc->is_valid, (GPid) -1);
+
 	if (!((doc != NULL && !EMPTY(doc->file_name)) || !EMPTY(dir)))
 	{
 		geany_debug("Failed to run command with no working directory");
@@ -942,7 +948,7 @@ static GPid build_run_cmd(GeanyDocument *doc, guint cmdindex)
 	gchar *vte_cmd_nonscript = NULL;
 	GError *error = NULL;
 
-	if (doc == NULL || doc->file_name == NULL)
+	if (! DOC_VALID(doc) || doc->file_name == NULL)
 		return (GPid) 0;
 
 	working_dir = prepare_run_script(doc, &vte_cmd_nonscript, cmdindex);
@@ -1583,6 +1589,8 @@ void build_menu_update(GeanyDocument *doc)
 	gboolean can_compile, can_build, can_make, run_sensitivity = FALSE, run_running = FALSE;
 	GeanyBuildCommand *bc;
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (menu_items.menu == NULL)
 		create_build_menu(&menu_items);
 	if (doc == NULL)
@@ -1977,6 +1985,8 @@ static RowWidgets *build_add_dialog_row(GeanyDocument *doc, GtkTable *table, gui
 	guint column = 0;
 	gchar *text;
 
+	g_return_val_if_fail(doc == NULL || doc->is_valid, NULL);
+
 	text = g_strdup_printf("%d.", cmd + 1);
 	label = gtk_label_new(text);
 	g_free(text);
diff --git a/src/dialogs.c b/src/dialogs.c
index 02976e7d..0d88a6f6 100644
--- a/src/dialogs.c
+++ b/src/dialogs.c
@@ -591,7 +591,7 @@ static gboolean show_save_as_gtk(GeanyDocument *doc)
 	GtkWidget *dialog;
 	gint resp;
 
-	g_return_val_if_fail(doc != NULL, FALSE);
+	g_return_val_if_fail(DOC_VALID(doc), FALSE);
 
 	dialog = create_save_file_dialog(doc);
 
@@ -1172,6 +1172,8 @@ void dialogs_show_file_properties(GeanyDocument *doc)
 # define S_IXOTH 0
 #endif
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (doc == NULL || doc->file_name == NULL)
 	{
 		dialogs_show_msgbox(GTK_MESSAGE_ERROR,
diff --git a/src/document.c b/src/document.c
index 14b7643e..a5801f2c 100644
--- a/src/document.c
+++ b/src/document.c
@@ -1099,6 +1099,8 @@ GeanyDocument *document_open_file_full(GeanyDocument *doc, const gchar *filename
 	GeanyFiletype *use_ft;
 	FileData filedata;
 
+	g_return_val_if_fail(doc == NULL || doc->is_valid, NULL);
+
 	if (reload)
 	{
 		utf8_filename = g_strdup(doc->file_name);
diff --git a/src/filetypes.c b/src/filetypes.c
index 0048b345..758426e6 100644
--- a/src/filetypes.c
+++ b/src/filetypes.c
@@ -1056,6 +1056,8 @@ GeanyFiletype *filetypes_detect_from_document(GeanyDocument *doc)
 	gchar 			*lines[GEANY_FILETYPE_SEARCH_LINES + 1];
 	gint			 i;
 
+	g_return_val_if_fail(doc == NULL || doc->is_valid, filetypes[GEANY_FILETYPES_NONE]);
+
 	if (doc == NULL)
 		return filetypes[GEANY_FILETYPES_NONE];
 
diff --git a/src/keybindings.c b/src/keybindings.c
index 9d664448..983e2493 100644
--- a/src/keybindings.c
+++ b/src/keybindings.c
@@ -1041,6 +1041,8 @@ static void trigger_button_event(GtkWidget *widget, guint32 event_time)
  * notebook tab list. */
 static gboolean check_menu_key(GeanyDocument *doc, guint keyval, guint state, guint32 event_time)
 {
+	g_return_val_if_fail(doc == NULL || doc->is_valid, FALSE);
+
 	if ((keyval == GDK_Menu && state == 0) || (keyval == GDK_F10 && state == GDK_SHIFT_MASK))
 	{
 		GtkWidget *focusw = gtk_window_get_focus(GTK_WINDOW(main_widgets.window));
@@ -1585,8 +1587,7 @@ static gboolean cb_func_build_action(guint key_id)
 
 static gboolean read_current_word(GeanyDocument *doc, gboolean sci_word)
 {
-	if (doc == NULL)
-		return FALSE;
+	g_return_val_if_fail(DOC_VALID(doc), FALSE);
 
 	if (sci_word)
 	{
@@ -1820,8 +1821,7 @@ static void goto_matching_brace(GeanyDocument *doc)
 	gint pos, new_pos;
 	gint after_brace;
 
-	if (doc == NULL)
-		return;
+	g_return_if_fail(DOC_VALID(doc));
 
 	pos = sci_get_current_position(doc->editor->sci);
 	after_brace = pos > 0 && utils_isbrace(sci_get_char_at(doc->editor->sci, pos - 1), TRUE);
diff --git a/src/navqueue.c b/src/navqueue.c
index 1df31da8..b6d64fb3 100644
--- a/src/navqueue.c
+++ b/src/navqueue.c
@@ -150,7 +150,8 @@ gboolean navqueue_goto_line(GeanyDocument *old_doc, GeanyDocument *new_doc, gint
 {
 	gint pos;
 
-	g_return_val_if_fail(new_doc != NULL, FALSE);
+	g_return_val_if_fail(old_doc == NULL || old_doc->is_valid, FALSE);
+	g_return_val_if_fail(DOC_VALID(new_doc), FALSE);
 	g_return_val_if_fail(line >= 1, FALSE);
 
 	pos = sci_get_position_from_line(new_doc->editor->sci, line - 1);
diff --git a/src/printing.c b/src/printing.c
index 9d77f3c5..743cd880 100644
--- a/src/printing.c
+++ b/src/printing.c
@@ -624,8 +624,7 @@ static void print_external(GeanyDocument *doc)
 
 void printing_print_doc(GeanyDocument *doc)
 {
-	if (doc == NULL)
-		return;
+	g_return_if_fail(DOC_VALID(doc));
 
 	if (printing_prefs.use_gtk_printing)
 		printing_print_gtk(doc);
diff --git a/src/search.c b/src/search.c
index 6710f079..6641b4e9 100644
--- a/src/search.c
+++ b/src/search.c
@@ -394,7 +394,7 @@ void search_find_selection(GeanyDocument *doc, gboolean search_backwards)
 {
 	gchar *s = NULL;
 
-	g_return_if_fail(doc != NULL);
+	g_return_if_fail(DOC_VALID(doc));
 
 #ifdef G_OS_UNIX
 	if (search_prefs.find_selection_type == GEANY_FIND_SEL_X)
@@ -1225,7 +1225,7 @@ gint search_mark_all(GeanyDocument *doc, const gchar *search_text, gint flags)
 	struct Sci_TextToFind ttf;
 	GSList *match, *matches;
 
-	g_return_val_if_fail(doc != NULL, 0);
+	g_return_val_if_fail(DOC_VALID(doc), 0);
 
 	/* clear previous search indicators */
 	editor_indicator_clear(doc->editor, GEANY_INDICATOR_SEARCH);
@@ -2134,7 +2134,7 @@ static gint find_document_usage(GeanyDocument *doc, const gchar *search_text, gi
 	gint prev_line = -1;
 	GSList *match, *matches;
 
-	g_return_val_if_fail(doc != NULL, 0);
+	g_return_val_if_fail(DOC_VALID(doc), 0);
 
 	short_file_name = g_path_get_basename(DOC_FILENAME(doc));
 
diff --git a/src/sidebar.c b/src/sidebar.c
index a2685992..46d1b01e 100644
--- a/src/sidebar.c
+++ b/src/sidebar.c
@@ -187,6 +187,8 @@ void sidebar_update_tag_list(GeanyDocument *doc, gboolean update)
 {
 	GtkWidget *child = gtk_bin_get_child(GTK_BIN(tag_window));
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	/* changes the tree view to the given one, trying not to do useless changes */
 	#define CHANGE_TREE(new_child) \
 		G_STMT_START { \
diff --git a/src/symbols.c b/src/symbols.c
index f03626fd..03df2940 100644
--- a/src/symbols.c
+++ b/src/symbols.c
@@ -1715,7 +1715,7 @@ gboolean symbols_recreate_tag_list(GeanyDocument *doc, gint sort_mode)
 {
 	GList *tags;
 
-	g_return_val_if_fail(doc != NULL, FALSE);
+	g_return_val_if_fail(DOC_VALID(doc), FALSE);
 
 	tags = get_tag_list(doc, tm_tag_max_t);
 	if (tags == NULL)
@@ -2226,6 +2226,8 @@ static gint get_current_tag_name_cached(GeanyDocument *doc, const gchar **tagnam
 	static gint tag_line = -1;
 	static gchar *cur_tag = NULL;
 
+	g_return_val_if_fail(doc == NULL || doc->is_valid, -1);
+
 	if (doc == NULL)	/* reset current function */
 	{
 		current_tag_changed(NULL, -1, -1, 0);
diff --git a/src/templates.c b/src/templates.c
index 334d0538..4233c0d0 100644
--- a/src/templates.c
+++ b/src/templates.c
@@ -107,6 +107,8 @@ static void convert_eol_characters(GString *template, GeanyDocument *doc)
 {
 	gint doc_eol_mode;
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (doc == NULL)
 		doc = document_get_current();
 
@@ -436,7 +438,7 @@ gchar *templates_get_template_licence(GeanyDocument *doc, gint licence_type)
 {
 	GString *template;
 
-	g_return_val_if_fail(doc != NULL, NULL);
+	g_return_val_if_fail(DOC_VALID(doc), NULL);
 	g_return_val_if_fail(licence_type == GEANY_TEMPLATE_GPL || licence_type == GEANY_TEMPLATE_BSD, NULL);
 
 	template = g_string_new(templates[licence_type]);
@@ -502,9 +504,13 @@ gchar *templates_get_template_function(GeanyDocument *doc, const gchar *func_nam
 
 gchar *templates_get_template_changelog(GeanyDocument *doc)
 {
-	GString *result = g_string_new(templates[GEANY_TEMPLATE_CHANGELOG]);
-	const gchar *file_type_name = (doc != NULL) ? doc->file_type->name : "";
+	GString *result;
+	const gchar *file_type_name;
 
+	g_return_val_if_fail(DOC_VALID(doc), NULL);
+
+	result = g_string_new(templates[GEANY_TEMPLATE_CHANGELOG]);
+	file_type_name = (doc->file_type != NULL) ? doc->file_type->name : "";
 	replace_static_values(result);
 	templates_replace_default_dates(result);
 	templates_replace_command(result, DOC_FILENAME(doc), file_type_name, NULL);
diff --git a/src/tools.c b/src/tools.c
index 5ac080da..607d5f47 100644
--- a/src/tools.c
+++ b/src/tools.c
@@ -356,7 +356,7 @@ void tools_execute_custom_command(GeanyDocument *doc, const gchar *command)
 	gint stdout_fd;
 	gint stderr_fd;
 
-	g_return_if_fail(doc != NULL && command != NULL);
+	g_return_if_fail(DOC_VALID(doc) && command != NULL);
 
 	if (! sci_has_selection(doc->editor->sci))
 		editor_select_lines(doc->editor, FALSE);
@@ -697,7 +697,7 @@ static void cc_on_custom_command_activate(GtkMenuItem *menuitem, gpointer user_d
 	GeanyDocument *doc = document_get_current();
 	gint command_idx;
 
-	g_return_if_fail(doc != NULL);
+	g_return_if_fail(DOC_VALID(doc));
 
 	command_idx = GPOINTER_TO_INT(user_data);
 
diff --git a/src/ui_utils.c b/src/ui_utils.c
index f1f31cdc..381ec57d 100644
--- a/src/ui_utils.c
+++ b/src/ui_utils.c
@@ -317,6 +317,8 @@ static gchar *create_statusbar_statistics(GeanyDocument *doc,
 /* updates the status bar document statistics */
 void ui_update_statusbar(GeanyDocument *doc, gint pos)
 {
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (! interface_prefs.statusbar_visible)
 		return; /* just do nothing if statusbar is not visible */
 
@@ -359,6 +361,8 @@ void ui_set_window_title(GeanyDocument *doc)
 	GString *str;
 	GeanyProject *project = app->project;
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (doc == NULL)
 		doc = document_get_current();
 
@@ -445,6 +449,8 @@ void ui_update_popup_reundo_items(GeanyDocument *doc)
 	gboolean enable_redo;
 	guint i, len;
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (doc == NULL)
 	{
 		enable_undo = FALSE;
@@ -475,6 +481,8 @@ void ui_update_popup_copy_items(GeanyDocument *doc)
 	gboolean enable;
 	guint i, len;
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (doc == NULL)
 		enable = FALSE;
 	else
@@ -501,6 +509,8 @@ void ui_update_menu_copy_items(GeanyDocument *doc)
 	guint i, len;
 	GtkWidget *focusw = gtk_window_get_focus(GTK_WINDOW(main_widgets.window));
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (IS_SCINTILLA(focusw))
 		enable = (doc == NULL) ? FALSE : sci_has_selection(doc->editor->sci);
 	else
@@ -524,6 +534,8 @@ void ui_update_insert_include_item(GeanyDocument *doc, gint item)
 {
 	gboolean enable = FALSE;
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (doc == NULL || doc->file_type == NULL)
 		enable = FALSE;
 	else if (doc->file_type->id == GEANY_FILETYPES_C ||  doc->file_type->id == GEANY_FILETYPES_CPP)
@@ -892,6 +904,8 @@ void ui_document_show_hide(GeanyDocument *doc)
 	GtkWidget *item;
 	const GeanyIndentPrefs *iprefs;
 
+	g_return_if_fail(doc == NULL || doc->is_valid);
+
 	if (doc == NULL)
 		doc = document_get_current();