diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index e107c5e..d46f819 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -5744,12 +5744,16 @@
 	    }
 	}
 
-	// temporarily zero terminate substring, print, restore char, wrap
-	backup_ch = *(cs + slen);
-	*(cs + slen) = 0;
+	if (slen < len)
+	{
+	    // temporarily zero terminate substring, print, restore char, wrap
+	    backup_ch = *(cs + slen);
+	    *(cs + slen) = NUL;
+	}
 	len_sum += gui_gtk2_draw_string_ext(row, col + len_sum,
 						 cs, slen, flags, needs_pango);
-	*(cs + slen) = backup_ch;
+	if (slen < len)
+	    *(cs + slen) = backup_ch;
 	cs += slen;
 	byte_sum += slen;
 	needs_pango = should_need_pango;