diff --git a/fpdfsdk/cpdfsdk_appstream.cpp b/fpdfsdk/cpdfsdk_appstream.cpp
index a0fc3b0..8157314 100644
--- a/fpdfsdk/cpdfsdk_appstream.cpp
+++ b/fpdfsdk/cpdfsdk_appstream.cpp
@@ -1115,27 +1115,26 @@
   pImageDict->SetNewFor<CPDF_String>("Name", name, false);
 }
 
-CheckStyle CheckStyleFromCaption(const WideString& caption,
-                                 CheckStyle default_style) {
+Optional<CheckStyle> CheckStyleFromCaption(const WideString& caption) {
   if (caption.IsEmpty())
-    return default_style;
+    return pdfium::nullopt;
 
   // Character values are ZapfDingbats encodings of named glyphs.
   switch (caption[0]) {
     case L'4':
       return CheckStyle::kCheck;
-    case L'l':
-      return CheckStyle::kCircle;
     case L'8':
       return CheckStyle::kCross;
-    case L'u':
-      return CheckStyle::kDiamond;
-    case L'n':
-      return CheckStyle::kSquare;
     case L'H':
       return CheckStyle::kStar;
+    case L'l':
+      return CheckStyle::kCircle;
+    case L'n':
+      return CheckStyle::kSquare;
+    case L'u':
+      return CheckStyle::kDiamond;
     default:
-      return default_style;
+      return pdfium::nullopt;
   }
 }
 
@@ -1381,9 +1380,8 @@
     crText = CFX_Color(iColorType, fc[0], fc[1], fc[2], fc[3]);
   }
 
-  CheckStyle nStyle =
-      CheckStyleFromCaption(pControl->GetNormalCaption(),
-                            /*default_style=*/CheckStyle::kCheck);
+  CheckStyle nStyle = CheckStyleFromCaption(pControl->GetNormalCaption())
+                          .value_or(CheckStyle::kCheck);
   ByteString csAP_N_ON =
       GetRectFillAppStream(rcWindow, crBackground) +
       GetBorderAppStreamInternal(rcWindow, fBorderWidth, crBorder, crLeftTop,
@@ -1476,9 +1474,8 @@
     crText = CFX_Color(iColorType, fc[0], fc[1], fc[2], fc[3]);
   }
 
-  CheckStyle nStyle =
-      CheckStyleFromCaption(pControl->GetNormalCaption(),
-                            /*default_style=*/CheckStyle::kCircle);
+  CheckStyle nStyle = CheckStyleFromCaption(pControl->GetNormalCaption())
+                          .value_or(CheckStyle::kCircle);
 
   ByteString csAP_N_ON;
   CFX_FloatRect rcCenter = rcWindow.GetCenterSquare().GetDeflated(1.0f, 1.0f);