diff --git a/modules/rntuple.mjs b/modules/rntuple.mjs
index 1ca9570f7..a4b5a97f3 100644
--- a/modules/rntuple.mjs
+++ b/modules/rntuple.mjs
@@ -110,7 +110,21 @@ class RBufferReader {
 
 }
 
-
+// Envelope Types
+// TODO: Define usage logic for envelope types in future
+// const kEnvelopeTypeHeader = 0x01,
+//       kEnvelopeTypeFooter = 0x02,
+//       kEnvelopeTypePageList = 0x03,
+
+// Field Flags
+const kFlagRepetitiveField = 0x01,
+      kFlagProjectedField = 0x02,
+      kFlagHasTypeChecksum = 0x04,
+
+// Column Flags
+      kFlagDeferredColumn = 0x01,
+      kFlagHasValueRange = 0x02;
+      
 class RNTupleDescriptorBuilder {
 
     deserializeHeader(header_blob) {
@@ -246,9 +260,15 @@ class RNTupleDescriptorBuilder {
                 sourceFieldId = null,
                 checksum = null;
 
-            if (flags & 0x1) arraySize = reader.readU64();
-            if (flags & 0x2) sourceFieldId = reader.readU32();
-            if (flags & 0x4) checksum = reader.readU32();
+            if (flags & kFlagRepetitiveField)
+                arraySize = reader.readU64();
+
+            if (flags & kFlagProjectedField)
+                sourceFieldId = reader.readU32();
+            
+            if (flags & kFlagHasTypeChecksum)
+                checksum = reader.readU32();
+
 
             fieldDescriptors.push({
                 fieldVersion,
@@ -289,8 +309,11 @@ class RNTupleDescriptorBuilder {
             let firstElementIndex = null,
                 minValue = null,
                 maxValue = null;
-            if (flags & 0x1) firstElementIndex = reader.readU64();
-            if (flags & 0x2) {
+
+            if (flags & kFlagDeferredColumn)
+                firstElementIndex = reader.readU64();
+            
+            if (flags & kFlagHasValueRange) {
                 minValue = reader.readF64();
                 maxValue = reader.readF64();
             }
@@ -307,7 +330,7 @@ class RNTupleDescriptorBuilder {
                 maxValue
             };
             column.isDeferred = function() {
-                return (this.flags & 0x01) !== 0;
+                return (this.flags & RNTupleDescriptorBuilder.kFlagDeferredColumn) !== 0;
             };
             column.isSuppressed = function() {
                 return this.firstElementIndex !== null && this.firstElementIndex < 0;