diff -r 6575679d2e8e -r 8a668d0a0d10 plover-gtk/transactionhelper.c
--- a/plover-gtk/transactionhelper.c	Fri Jun 08 14:48:00 2018 +0100
+++ b/plover-gtk/transactionhelper.c	Wed Sep 12 17:12:06 2018 +0100
@@ -668,8 +668,8 @@
       (prefix[strlen(alt)]=='\0' || prefix[strlen(alt)]=='/');
 }
 
-static gboolean
-  plover_transaction_helper_check_vendor(PloverTransactionHelper *helper,
+static void
+  plover_transaction_helper_update_summary_page(PloverTransactionHelper *helper,
   GError **error)
 {
     int i,remove_count=0;
@@ -682,11 +682,12 @@
     GtkWidget *container,*summary,*page;
     GtkButton *button;
     GtkLabel *label;
-    g_return_val_if_fail(PLOVER_IS_TRANSACTION_HELPER(helper),FALSE);
+    g_return_if_fail(PLOVER_IS_TRANSACTION_HELPER(helper));
     comps=plover_transaction_helper_get_comps(helper,error);
-    if (!comps)
-	return FALSE;
-    prefix=plover_comps_get_default_prefix(comps);
+    if (comps)
+	prefix=plover_comps_get_default_prefix(comps);
+    else
+	prefix=NULL;
     button=GTK_BUTTON(gtk_builder_get_object(helper->ui,"SIRemoveExisting"));
     gtk_toggle_button_set_active(GTK_TOGGLE_BUTTON(button),FALSE);
     container=GTK_WIDGET(gtk_builder_get_object(helper->ui,
@@ -721,6 +722,7 @@
     }
     if (alternate_database_clashes || active_database_is_incompatible)
     {
+	g_assert(comps!=NULL);
 	label=GTK_LABEL(gtk_builder_get_object(helper->ui,
 	  "SIIncompatibleInstallationLabel"));
 	if (alternate_database_clashes)
@@ -753,7 +755,6 @@
 	    gtk_assistant_set_page_complete(helper->assistant,page,TRUE);
     }
     g_free(prefix);
-    return TRUE;
 }
 
 void plover_transaction_helper_set_check_vendor(PloverTransactionHelper *helper,
@@ -764,7 +765,7 @@
     {
 	helper->check_vendor=check_vendor;
 	if (helper->transactions)
-	    plover_transaction_helper_check_vendor(helper,NULL);
+	    plover_transaction_helper_update_summary_page(helper,NULL);
     }
 }
 
@@ -868,7 +869,7 @@
 	return FALSE;
     }
     if (!helper->transactions)
-	plover_transaction_helper_check_vendor(helper,error);
+	plover_transaction_helper_update_summary_page(helper,error);
     g_object_ref(transaction);
     helper->transactions=g_slist_append(helper->transactions,transaction);
     if (report_action==PLOVER_TRANSACTION_HELPER_REPORT_REMOVE)