diff --git a/src/dispnew.c b/src/dispnew.c
index b786f0f1ba4..2568ba1086a 100644
--- a/src/dispnew.c
+++ b/src/dispnew.c
@@ -1810,9 +1810,12 @@ allocate_matrices_for_window_redisplay (struct window *w)
 	  if (w->desired_matrix == NULL)
 	    {
 	      w->desired_matrix = new_glyph_matrix (NULL);
-	      w->current_matrix = new_glyph_matrix (NULL);
+	      eassert (w->current_matrix == NULL);
 	    }
 
+	  if (w->current_matrix == NULL)
+	    w->current_matrix = new_glyph_matrix (NULL);
+
 	  dim.width = required_matrix_width (w);
 	  dim.height = required_matrix_height (w);
 	  adjust_glyph_matrix (w, w->desired_matrix, 0, 0, dim);