diff --git a/src/scheduler.c b/src/scheduler.c
index 590c4140..191b2fa4 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -3361,8 +3361,8 @@ int xschem(ClientData clientdata, Tcl_Interp *interp, int argc, const char * arg
     else if(!strcmp(argv[1], "preview_window"))
     {
       if(!xctx) {Tcl_SetResult(interp, not_avail, TCL_STATIC); return TCL_ERROR;}
-      if(argc == 3) preview_window(argv[2], "{}", "{}");
-      else if(argc == 4) preview_window(argv[2], argv[3], "{}");
+      if(argc == 3) preview_window(argv[2], "", NULL);
+      else if(argc == 4) preview_window(argv[2], argv[3], NULL);
       else if(argc == 5) {
         char f[PATH_MAX + 100];
         my_snprintf(f, S(f),"regsub {^~/} {%s} {%s/}", argv[4], home_dir);
diff --git a/src/xinit.c b/src/xinit.c
index b330eed5..1058d531 100644
--- a/src/xinit.c
+++ b/src/xinit.c
@@ -1206,7 +1206,7 @@ void preview_window(const char *what, const char *win_path, const char *fname)
     dbg(1, "preview_window() draw\n");
     save_xctx = xctx; /* save current schematic */
     xctx = preview_xctx;
-    if(!current_file || strcmp(fname, current_file) ) { 
+    if(fname && fname[0] && (!current_file || strcmp(fname, current_file)) ) { 
       if(current_file) {
         delete_schematic_data(1);
       }
@@ -1229,21 +1229,23 @@ void preview_window(const char *what, const char *win_path, const char *fname)
     xctx = save_xctx;
   }
   else if(!strcmp(what, "destroy") || !strcmp(what, "close")) {
-    dbg(1, "preview_window() destroy\n");
-    save_xctx = xctx; /* save current schematic */
-    xctx = preview_xctx;
-    if(current_file) {
-      delete_schematic_data(1);
-      preview_xctx = NULL;
+    dbg(1, "preview_window(): %s\n", what);
+    if(preview_xctx) {
+      save_xctx = xctx; /* save current schematic */
+      xctx = preview_xctx;
+      if(current_file) {
+        delete_schematic_data(1);
+        preview_xctx = NULL;
+      }
+      my_free(_ALLOC_ID_, &current_file);
+      xctx = save_xctx; /* restore schematic */
+      save_xctx = NULL;
+      set_modify(-1);
     }
     if(!strcmp(what, "destroy")) {
       Tk_DestroyWindow(tkpre_window);
       tkpre_window = NULL;
     }
-    my_free(_ALLOC_ID_, &current_file);
-    xctx = save_xctx; /* restore schematic */
-    save_xctx = NULL;
-    set_modify(-1);
   }
   tclvareval("restore_ctx ", xctx->current_win_path, NULL);
   semaphore--;