diff --git a/fpdfsdk/fpdf_annot.cpp b/fpdfsdk/fpdf_annot.cpp
index ddedcf1..8545459 100644
--- a/fpdfsdk/fpdf_annot.cpp
+++ b/fpdfsdk/fpdf_annot.cpp
@@ -314,12 +314,23 @@
 FPDF_EXPORT FPDF_BOOL FPDF_CALLCONV
 FPDFAnnot_IsSupportedSubtype(FPDF_ANNOTATION_SUBTYPE subtype) {
   // The supported subtypes must also be communicated in the user doc.
-  return subtype == FPDF_ANNOT_CIRCLE || subtype == FPDF_ANNOT_FREETEXT ||
-         subtype == FPDF_ANNOT_HIGHLIGHT || subtype == FPDF_ANNOT_INK ||
-         subtype == FPDF_ANNOT_LINK || subtype == FPDF_ANNOT_POPUP ||
-         subtype == FPDF_ANNOT_SQUARE || subtype == FPDF_ANNOT_SQUIGGLY ||
-         subtype == FPDF_ANNOT_STAMP || subtype == FPDF_ANNOT_STRIKEOUT ||
-         subtype == FPDF_ANNOT_TEXT || subtype == FPDF_ANNOT_UNDERLINE;
+  switch (subtype) {
+    case FPDF_ANNOT_CIRCLE:
+    case FPDF_ANNOT_FREETEXT:
+    case FPDF_ANNOT_HIGHLIGHT:
+    case FPDF_ANNOT_INK:
+    case FPDF_ANNOT_LINK:
+    case FPDF_ANNOT_POPUP:
+    case FPDF_ANNOT_SQUARE:
+    case FPDF_ANNOT_SQUIGGLY:
+    case FPDF_ANNOT_STAMP:
+    case FPDF_ANNOT_STRIKEOUT:
+    case FPDF_ANNOT_TEXT:
+    case FPDF_ANNOT_UNDERLINE:
+      return true;
+    default:
+      return false;
+  }
 }
 
 FPDF_EXPORT FPDF_ANNOTATION FPDF_CALLCONV
diff --git a/public/fpdf_annot.h b/public/fpdf_annot.h
index e4729ce..04e411a 100644
--- a/public/fpdf_annot.h
+++ b/public/fpdf_annot.h
@@ -91,8 +91,19 @@
 
 // Experimental API.
 // Check if an annotation subtype is currently supported for creation.
-// Currently supported subtypes: circle, highlight, ink, link, popup, square,
-// squiggly, stamp, strikeout, text, and underline.
+// Currently supported subtypes:
+//    - circle
+//    - freetext
+//    - highlight
+//    - ink
+//    - link
+//    - popup
+//    - square,
+//    - squiggly
+//    - stamp
+//    - strikeout
+//    - text
+//    - underline
 //
 //   subtype   - the subtype to be checked.
 //