diff --git a/SourceGen/AsmGen/AsmTass64.cs b/SourceGen/AsmGen/AsmTass64.cs
index 29300cc..b20c3ef 100644
--- a/SourceGen/AsmGen/AsmTass64.cs
+++ b/SourceGen/AsmGen/AsmTass64.cs
@@ -309,22 +309,6 @@ namespace SourceGen.AsmGen {
             }
         }
 
-        private CharEncoding.Encoding FormatDescriptorToCharEncoding(FormatDescriptor dfd) {
-            switch (dfd.FormatSubType) {
-                case FormatDescriptor.SubType.Ascii:
-                    return CharEncoding.Encoding.Ascii;
-                case FormatDescriptor.SubType.HighAscii:
-                    return CharEncoding.Encoding.HighAscii;
-                case FormatDescriptor.SubType.C64Petscii:
-                    return CharEncoding.Encoding.C64Petscii;
-                case FormatDescriptor.SubType.C64Screen:
-                    return CharEncoding.Encoding.C64ScreenCode;
-                case FormatDescriptor.SubType.ASCII_GENERIC:
-                default:
-                    return CharEncoding.Encoding.Unknown;
-            }
-        }
-
         // IGenerator
         public string ModifyOpcode(int offset, OpDef op) {
             if (op.IsUndocumented) {
@@ -358,7 +342,7 @@ namespace SourceGen.AsmGen {
 
         // IGenerator
         public void UpdateCharacterEncoding(FormatDescriptor dfd) {
-            CharEncoding.Encoding newEnc = FormatDescriptorToCharEncoding(dfd);
+            CharEncoding.Encoding newEnc = PseudoOp.SubTypeToEnc(dfd.FormatSubType);
             if (newEnc == CharEncoding.Encoding.Unknown) {
                 // probably not a character operand
                 return;
diff --git a/SourceGen/PseudoOp.cs b/SourceGen/PseudoOp.cs
index 222b61a..4d5756c 100644
--- a/SourceGen/PseudoOp.cs
+++ b/SourceGen/PseudoOp.cs
@@ -499,6 +499,12 @@ namespace SourceGen {
             HasHashPrefix,      // operand has a leading '#', avoiding ambiguity in some cases
         }
 
+        /// <summary>
+        /// Converts a FormatDescriptor SubType to a CharEncoding.Encoding value.
+        /// </summary>
+        /// <param name="subType">FormatDescriptor sub-type.</param>
+        /// <returns>The corresponding CharEncoding.Encoding value, or Encoding.Unknown
+        ///   if the sub-type isn't a character encoding.</returns>
         public static CharEncoding.Encoding SubTypeToEnc(FormatDescriptor.SubType subType) {
             switch (subType) {
                 case FormatDescriptor.SubType.Ascii: