1 files changed, 9 insertions, 4 deletions

diff --git a/src/w32term.c b/src/w32term.c
index db4ccf58138..ac29bbbbd46 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -6922,10 +6922,15 @@ w32_initialize_display_info (Lisp_Object display_name)
   memset (dpyinfo, 0, sizeof (*dpyinfo));
 
   dpyinfo->name_list_element = Fcons (display_name, Qnil);
-  dpyinfo->w32_id_name = xmalloc (SCHARS (Vinvocation_name)
-                                  + SCHARS (Vsystem_name) + 2);
-  sprintf (dpyinfo->w32_id_name, "%s@%s",
-           SDATA (Vinvocation_name), SDATA (Vsystem_name));
+  if (STRINGP (Vsystem_name))
+    {
+      dpyinfo->w32_id_name = xmalloc (SCHARS (Vinvocation_name)
+                                      + SCHARS (Vsystem_name) + 2);
+      sprintf (dpyinfo->w32_id_name, "%s@%s",
+               SDATA (Vinvocation_name), SDATA (Vsystem_name));
+    }
+  else
+    dpyinfo->w32_id_name = xlispstrdup (Vinvocation_name);
 
   /* Default Console mode values - overridden when running in GUI mode
      with values obtained from system metrics.  */