diff --git a/dlls/jscript/dispex.c b/dlls/jscript/dispex.c
index 81df4d02655..63ab21d2fb2 100644
--- a/dlls/jscript/dispex.c
+++ b/dlls/jscript/dispex.c
@@ -216,7 +216,11 @@ static HRESULT find_prop_name(jsdisp_t *This, unsigned hash, const WCHAR *name,
 
     builtin = find_builtin_prop(This, name);
     if(builtin) {
-        prop = alloc_prop(This, name, PROP_BUILTIN, builtin->flags);
+        unsigned flags = builtin->flags;
+        if(flags & PROPF_METHOD)
+            flags |= PROPF_CONFIGURABLE;
+        flags &= PROPF_ENUM | PROPF_CONST | PROPF_CONFIGURABLE;
+        prop = alloc_prop(This, name, PROP_BUILTIN, flags);
         if(!prop)
             return E_OUTOFMEMORY;
 
@@ -485,7 +489,7 @@ static HRESULT prop_put(jsdisp_t *This, dispex_prop_t *prop, jsval_t val)
         /* fall through */
     case PROP_PROTREF:
         prop->type = PROP_JSVAL;
-        prop->flags = PROPF_ENUM;
+        prop->flags = PROPF_ENUM | PROPF_CONFIGURABLE;
         prop->u.val = jsval_undefined();
         break;
     case PROP_JSVAL:
@@ -744,7 +748,7 @@ static HRESULT WINAPI DispatchEx_InvokeEx(IDispatchEx *iface, DISPID id, LCID lc
 
 static HRESULT delete_prop(dispex_prop_t *prop, BOOL *ret)
 {
-    if(prop->flags & PROPF_DONTDELETE) {
+    if(!(prop->flags & PROPF_CONFIGURABLE)) {
         *ret = FALSE;
         return S_OK;
     }
@@ -1035,7 +1039,7 @@ HRESULT jsdisp_get_id(jsdisp_t *jsdisp, const WCHAR *name, DWORD flags, DISPID *
     HRESULT hres;
 
     if(flags & fdexNameEnsure)
-        hres = ensure_prop_name(jsdisp, name, TRUE, PROPF_ENUM, &prop);
+        hres = ensure_prop_name(jsdisp, name, TRUE, PROPF_ENUM | PROPF_CONFIGURABLE, &prop);
     else
         hres = find_prop_name_prot(jsdisp, string_hash(name), name, &prop);
     if(FAILED(hres))
@@ -1307,7 +1311,7 @@ HRESULT jsdisp_propput(jsdisp_t *obj, const WCHAR *name, DWORD flags, jsval_t va
 
 HRESULT jsdisp_propput_name(jsdisp_t *obj, const WCHAR *name, jsval_t val)
 {
-    return jsdisp_propput(obj, name, PROPF_ENUM, val);
+    return jsdisp_propput(obj, name, PROPF_ENUM | PROPF_CONFIGURABLE, val);
 }
 
 HRESULT jsdisp_propput_const(jsdisp_t *obj, const WCHAR *name, jsval_t val)
@@ -1324,7 +1328,7 @@ HRESULT jsdisp_propput_const(jsdisp_t *obj, const WCHAR *name, jsval_t val)
 
 HRESULT jsdisp_propput_dontenum(jsdisp_t *obj, const WCHAR *name, jsval_t val)
 {
-    return jsdisp_propput(obj, name, 0, val);
+    return jsdisp_propput(obj, name, PROPF_CONFIGURABLE, val);
 }
 
 HRESULT jsdisp_propput_idx(jsdisp_t *obj, DWORD idx, jsval_t val)
diff --git a/dlls/jscript/function.c b/dlls/jscript/function.c
index 8480a3bf1a0..2e905a993b0 100644
--- a/dlls/jscript/function.c
+++ b/dlls/jscript/function.c
@@ -184,7 +184,7 @@ HRESULT setup_arguments_object(script_ctx_t *ctx, call_frame_t *frame)
     if(SUCCEEDED(hres))
         hres = jsdisp_propput_dontenum(&args->jsdisp, caleeW, jsval_disp(to_disp(&args->function->dispex)));
     if(SUCCEEDED(hres))
-        hres = jsdisp_propput(frame->base_scope->jsobj, argumentsW, PROPF_DONTDELETE, jsval_obj(&args->jsdisp));
+        hres = jsdisp_propput(frame->base_scope->jsobj, argumentsW, 0, jsval_obj(&args->jsdisp));
     if(FAILED(hres)) {
         jsdisp_release(&args->jsdisp);
         return hres;
diff --git a/dlls/jscript/jscript.h b/dlls/jscript/jscript.h
index 86786192489..03a96c3e723 100644
--- a/dlls/jscript/jscript.h
+++ b/dlls/jscript/jscript.h
@@ -87,12 +87,12 @@ typedef struct jsdisp_t jsdisp_t;
 
 extern HINSTANCE jscript_hinstance DECLSPEC_HIDDEN;
 
-#define PROPF_ARGMASK     0x00ff
-#define PROPF_METHOD      0x0100
-#define PROPF_ENUM        0x0200
-#define PROPF_CONSTR      0x0400
-#define PROPF_CONST       0x0800
-#define PROPF_DONTDELETE  0x1000
+#define PROPF_ARGMASK       0x00ff
+#define PROPF_METHOD        0x0100
+#define PROPF_ENUM          0x0200
+#define PROPF_CONSTR        0x0400
+#define PROPF_CONST         0x0800
+#define PROPF_CONFIGURABLE  0x1000
 
 #define PROPF_VERSION_MASK  0x01ff0000
 #define PROPF_VERSION_SHIFT 16