diff --git a/dll/directx/wine/d3dx9_36/font.c b/dll/directx/wine/d3dx9_36/font.c
index 89005ce..05e490f 100644
--- a/dll/directx/wine/d3dx9_36/font.c
+++ b/dll/directx/wine/d3dx9_36/font.c
@@ -235,7 +235,7 @@ static INT WINAPI ID3DXFontImpl_DrawTextW(ID3DXFont *iface, ID3DXSprite *sprite,
         const WCHAR *string, INT count, RECT *rect, DWORD format, D3DCOLOR color)
 {
     struct d3dx_font *This = impl_from_ID3DXFont(iface);
-    RECT calc_rect = *rect;
+    RECT calc_rect;
     INT height;
 
     TRACE("iface %p, sprite %p, string %s, count %d, rect %s, format %#x, color 0x%08x\n",
@@ -251,11 +251,15 @@ static INT WINAPI ID3DXFontImpl_DrawTextW(ID3DXFont *iface, ID3DXSprite *sprite,
     while (count > 0 && !string[count-1])
         count--;
 
+    if (rect)
+        calc_rect = *rect;
+
     height = DrawTextW(This->hdc, string, count, &calc_rect, format | DT_CALCRECT);
 
     if (format & DT_CALCRECT)
     {
-        *rect = calc_rect;
+        if (rect)
+            *rect = calc_rect;
         return height;
     }
 
diff --git a/modules/rostests/winetests/d3dx9_36/core.c b/modules/rostests/winetests/d3dx9_36/core.c
index 841d07e..a5abb79 100644
--- a/modules/rostests/winetests/d3dx9_36/core.c
+++ b/modules/rostests/winetests/d3dx9_36/core.c
@@ -662,6 +662,15 @@ static void test_ID3DXFont(IDirect3DDevice9 *device)
         height = ID3DXFont_DrawTextA(font, NULL, testA, 2, &rect, 0, 0xFF00FF);
         ok(height == 12, "DrawTextA returned %d, expected 12.\n", height);
 
+        height = ID3DXFont_DrawTextA(font, NULL, testA, -1, NULL, 0, 0xFF00FF);
+        ok(height == 12, "DrawTextA returned %d, expected 12.\n", height);
+
+        height = ID3DXFont_DrawTextA(font, NULL, testA, -1, NULL, DT_CALCRECT, 0xFF00FF);
+        ok(height == 12, "DrawTextA returned %d, expected 12.\n", height);
+
+        height = ID3DXFont_DrawTextA(font, NULL, NULL, -1, NULL, 0, 0xFF00FF);
+        ok(height == 0, "DrawTextA returned %d, expected 0.\n", height);
+
 if (0) { /* Causes a lockup on windows 7. */
         height = ID3DXFont_DrawTextW(font, NULL, testW, -2, &rect, 0, 0xFF00FF);
         ok(height == 12, "DrawTextW returned %d, expected 12.\n", height);
@@ -679,6 +688,15 @@ if (0) { /* Causes a lockup on windows 7. */
         height = ID3DXFont_DrawTextW(font, NULL, testW, 2, &rect, 0, 0xFF00FF);
         ok(height == 12, "DrawTextW returned %d, expected 12.\n", height);
 
+        height = ID3DXFont_DrawTextW(font, NULL, testW, -1, NULL, 0, 0xFF00FF);
+        ok(height == 12, "DrawTextA returned %d, expected 12.\n", height);
+
+        height = ID3DXFont_DrawTextW(font, NULL, testW, -1, NULL, DT_CALCRECT, 0xFF00FF);
+        ok(height == 12, "DrawTextA returned %d, expected 12.\n", height);
+
+        height = ID3DXFont_DrawTextW(font, NULL, NULL, -1, NULL, 0, 0xFF00FF);
+        ok(height == 0, "DrawTextA returned %d, expected 0.\n", height);
+
         ID3DXFont_Release(font);
     }
 }