diff --git a/dlls/riched20/tests/txtsrv.c b/dlls/riched20/tests/txtsrv.c
index 7ca6074587d..3cfd5e63753 100644
--- a/dlls/riched20/tests/txtsrv.c
+++ b/dlls/riched20/tests/txtsrv.c
@@ -705,7 +705,7 @@ static void _check_txgetnaturalsize(HRESULT res, LONG width, LONG height, HDC hd
     expected_width = expected_rect.right - expected_rect.left;
     expected_height = expected_rect.bottom - expected_rect.top;
     ok_(__FILE__,line)(res == S_OK, "ITextServices_TxGetNaturalSize failed: 0x%08x.\n", res);
-    ok_(__FILE__,line)(width >= expected_width && width <= expected_width + 1,
+    todo_wine ok_(__FILE__,line)(width >= expected_width && width <= expected_width + 1,
                        "got wrong width: %d, expected: %d {+1}.\n", width, expected_width);
     ok_(__FILE__,line)(height == expected_height, "got wrong height: %d, expected: %d.\n",
                        height, expected_height);
@@ -717,7 +717,7 @@ static void test_TxGetNaturalSize(void)
     ITextHost *host;
     HRESULT result;
     SIZEL extent;
-    static const WCHAR test_text[] = {'T','e','s','t','S','o','m','e','T','e','x','t',0};
+    static const WCHAR test_text[] = L"TestSomeText";
     LONG width, height;
     HDC hdcDraw;
     HWND hwnd;
@@ -752,7 +752,7 @@ static void test_TxGetNaturalSize(void)
     height = 0;
     result = ITextServices_TxGetNaturalSize(txtserv, DVASPECT_CONTENT, hdcDraw, NULL, NULL,
                                             TXTNS_FITTOCONTENT, &extent, &width, &height);
-    todo_wine CHECK_TXGETNATURALSIZE(result, width, height, hdcDraw, rect, test_text);
+    CHECK_TXGETNATURALSIZE(result, width, height, hdcDraw, rect, test_text);
 
     ReleaseDC(hwnd, hdcDraw);
     DestroyWindow(hwnd);
diff --git a/dlls/riched20/txtsrv.c b/dlls/riched20/txtsrv.c
index 79ade0f6117..5736964c1b1 100644
--- a/dlls/riched20/txtsrv.c
+++ b/dlls/riched20/txtsrv.c
@@ -366,14 +366,43 @@ DECLSPEC_HIDDEN HRESULT __thiscall fnTextSrv_TxGetBaseLinePos(ITextServices *ifa
 }
 
 DEFINE_THISCALL_WRAPPER(fnTextSrv_TxGetNaturalSize,36)
-DECLSPEC_HIDDEN HRESULT __thiscall fnTextSrv_TxGetNaturalSize(ITextServices *iface, DWORD dwAspect, HDC hdcDraw,
-                                                              HDC hicTargetDev, DVTARGETDEVICE *ptd, DWORD dwMode,
-                                                              const SIZEL *psizelExtent, LONG *pwidth, LONG *pheight)
+DECLSPEC_HIDDEN HRESULT __thiscall fnTextSrv_TxGetNaturalSize( ITextServices *iface, DWORD aspect, HDC draw,
+                                                               HDC target, DVTARGETDEVICE *td, DWORD mode,
+                                                               const SIZEL *extent, LONG *width, LONG *height )
 {
     struct text_services *services = impl_from_ITextServices( iface );
+    RECT rect;
+    HDC dc = draw;
+    BOOL rewrap = FALSE;
+    HRESULT hr;
 
-    FIXME( "%p: STUB\n", services );
-    return E_NOTIMPL;
+    TRACE( "%p: aspect %d, draw %p, target %p, td %p, mode %08x, extent %s, *width %d, *height %d\n", services,
+           aspect, draw, target, td, mode, wine_dbgstr_point( (POINT *)extent ), *width, *height );
+
+    if (aspect != DVASPECT_CONTENT || target || td || mode != TXTNS_FITTOCONTENT )
+        FIXME( "Many arguments are ignored\n" );
+
+    SetRect( &rect, 0, 0, *width, *height );
+
+    hr = update_client_rect( services, &rect );
+    if (FAILED( hr )) return hr;
+    if (hr == S_OK) rewrap = TRUE;
+
+    if (!dc && services->editor->in_place_active)
+        dc = ITextHost_TxGetDC( services->host );
+    if (!dc) return E_FAIL;
+
+    if (rewrap)
+    {
+        editor_mark_rewrap_all( services->editor );
+        wrap_marked_paras_dc( services->editor, dc, FALSE );
+    }
+
+    *width = services->editor->nTotalWidth;
+    *height = services->editor->nTotalLength;
+
+    if (!draw) ITextHost_TxReleaseDC( services->host, dc );
+    return S_OK;
 }
 
 DEFINE_THISCALL_WRAPPER(fnTextSrv_TxGetDropTarget,8)