diff --git a/src/Kafa/Reader/KafaReader.Col.cs b/src/Kafa/Reader/KafaReader.Col.cs
index 290339d..98f4373 100644
--- a/src/Kafa/Reader/KafaReader.Col.cs
+++ b/src/Kafa/Reader/KafaReader.Col.cs
@@ -1,5 +1,4 @@
-using System.Reflection.PortableExecutable;
-using System.Runtime.CompilerServices;
+using System.Runtime.CompilerServices;
 
 namespace nyingi.Kafa.Reader
 {
@@ -37,7 +36,7 @@ public Col(ColEnumerable colEnumerable, string columnName)
 
 
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public bool TryParse<T>(out T result) where T : ISpanParsable<T> => _colEnumerable.TryParse(Value, out result);
+            public bool TryParse<T>(out T? result) where T : ISpanParsable<T> => _colEnumerable.TryParse(Value, out result);
 
             public override string ToString()
             {
@@ -95,12 +94,12 @@ public ReadOnlySpan<char> ReadColSpan(int index)
             } 
 
 
-            public T Parse<T>(ReadOnlySpan<char> scanSpan) where T : ISpanParsable<T>
+            public readonly T Parse<T>(ReadOnlySpan<char> scanSpan) where T : ISpanParsable<T>
             {
                 return T.Parse(scanSpan, _reader.cultureInfo);
             }
 
-            public bool TryParse<T>(ReadOnlySpan<char> colValue, out T result) where T : ISpanParsable<T>
+            public readonly bool TryParse<T>(ReadOnlySpan<char> colValue, out T? result) where T : ISpanParsable<T>
             {
                 return T.TryParse(colValue, _reader.cultureInfo, out result);
             }
diff --git a/src/Kafa/Reader/KafaReader.cs b/src/Kafa/Reader/KafaReader.cs
index 0cb30b1..465e715 100644
--- a/src/Kafa/Reader/KafaReader.cs
+++ b/src/Kafa/Reader/KafaReader.cs
@@ -31,7 +31,7 @@ public KafaReader(in KafaReadState kafaReadState)
         public OrderedDictionary? Headers => _kafaReadState.Headers;
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ReadOnlyMemory<char> ReadRowSpan(int index, out int lastColMarkerIndex)
+        public readonly ReadOnlyMemory<char> ReadRowSpan(int index, out int lastColMarkerIndex)
         {
             lastColMarkerIndex = index + ColumnCount;
 
@@ -51,7 +51,7 @@ public ReadOnlyMemory<char> ReadRowSpan(int index, out int lastColMarkerIndex)
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public ReadOnlySpan<char> ReadColSpan(int startIndex, int lastIndex)
+        public readonly ReadOnlySpan<char> ReadColSpan(int startIndex, int lastIndex)
         {
             return _kafaReadState.Buffer.AsSpan(startIndex, lastIndex - startIndex);
         }