diff --git a/c/xlib/window.c b/c/xlib/window.c
index 862e5fd..d81d015 100644
--- a/c/xlib/window.c
+++ b/c/xlib/window.c
@@ -174,15 +174,12 @@ s48_value scx_Get_Window_Attributes(s48_value Xdisplay, s48_value Xwindow) {
   return res;
 }
 
-s48_value scx_Configure_Window (s48_value Xwindow, s48_value Xdisplay, 
-			    s48_value alist) {
+unsigned long AList_To_XWindowChanges(s48_value alist, XWindowChanges* WC) {
   unsigned long mask = 0;
-  XWindowChanges WC;
   s48_value l, p;
   char* cname;
   int cvalue;
   s48_value name, value;
-  
   for (l = alist; !S48_NULL_P(l); l = S48_CDR(l)) {
     p = S48_CAR(l);
     name = S48_CAR(p);
@@ -191,30 +188,37 @@ s48_value scx_Configure_Window (s48_value Xwindow, s48_value Xdisplay,
     cvalue = (int)s48_extract_integer(value); // only ints here
 
     if (strcmp(cname, "x") == 0) {
-      WC.x = cvalue;
+      WC->x = cvalue;
       mask |= CWX;
     } else if (strcmp(cname, "y") == 0) {
-      WC.y = cvalue;
+      WC->y = cvalue;
       mask |= CWY;
     } else if (strcmp(cname, "width") == 0) {
-      WC.width = cvalue;
+      WC->width = cvalue;
       mask |= CWWidth;
     } else if (strcmp(cname, "height") == 0) {
-      WC.height = cvalue;
+      WC->height = cvalue;
       mask |= CWHeight;
     } else if (strcmp(cname, "border-width") == 0) {
-      WC.border_width = cvalue;
+      WC->border_width = cvalue;
       mask |= CWBorderWidth;
     } else if (strcmp(cname, "sibling") == 0) {
-      WC.sibling = (Window)s48_extract_integer(value);
+      WC->sibling = (Window)s48_extract_integer(value);
       mask |= CWSibling;
     } else if (strcmp(cname, "stack-mode") == 0) {
-      WC.stack_mode = cvalue;
+      WC->stack_mode = cvalue;
       mask |= CWStackMode;
     }
   } // for
+  return mask;
+}
 
-  XConfigureWindow (SCX_EXTRACT_DISPLAY(Xdisplay),SCX_EXTRACT_WINDOW(Xwindow), 
+s48_value scx_Configure_Window (s48_value Xwindow, s48_value Xdisplay, 
+			    s48_value alist) {
+  XWindowChanges WC;
+  unsigned long mask = AList_To_XWindowChanges(alist, &WC);
+
+  XConfigureWindow (SCX_EXTRACT_DISPLAY(Xdisplay), SCX_EXTRACT_WINDOW(Xwindow), 
 		    mask, &WC);
   return S48_UNSPECIFIC;
 }