diff --git a/src/xfns.c b/src/xfns.c
index 4614b97ba1d..95932dbe345 100644
--- a/src/xfns.c
+++ b/src/xfns.c
@@ -331,12 +331,8 @@ x_set_frame_parameters (f, alist)
 
   /* Same here.  */
   Lisp_Object left, top;
-  
-  XSET (width,  Lisp_Int, FRAME_WIDTH  (f));
-  XSET (height, Lisp_Int, FRAME_HEIGHT (f));
 
-  XSET (top, Lisp_Int, f->display.x->top_pos);
-  XSET (left, Lisp_Int, f->display.x->left_pos);
+  width = height = top = left = Qnil;
 
   for (tail = alist; CONSP (tail); tail = Fcdr (tail))
     {
@@ -346,13 +342,16 @@ x_set_frame_parameters (f, alist)
       prop = Fcar (elt);
       val = Fcdr (elt);
 
-      if (EQ (prop, Qwidth))
+      /* Ignore all but the first set presented.  You're supposed to
+	 be able to append two parameter lists and have the first
+	 shadow the second.  */
+      if (EQ (prop, Qwidth) && NILP (width))
 	width = val;
-      else if (EQ (prop, Qheight))
+      else if (EQ (prop, Qheight) && NILP (height))
 	height = val;
-      else if (EQ (prop, Qtop))
+      else if (EQ (prop, Qtop) && NILP (top))
 	top = val;
-      else if (EQ (prop, Qleft))
+      else if (EQ (prop, Qleft) && NILP (left))
 	left = val;
       else
 	{
@@ -373,6 +372,12 @@ x_set_frame_parameters (f, alist)
   {
     Lisp_Object frame;
 
+    if (NILP (width))  XSET (width,  Lisp_Int, FRAME_WIDTH  (f));
+    if (NILP (height)) XSET (height, Lisp_Int, FRAME_HEIGHT (f));
+
+    if (NILP (top))    XSET (top, Lisp_Int, f->display.x->top_pos);
+    if (NILP (left))   XSET (left, Lisp_Int, f->display.x->left_pos);
+
     XSET (frame, Lisp_Frame, f);
     if (XINT (width) != FRAME_WIDTH (f)
 	|| XINT (height) != FRAME_HEIGHT (f))