diff --git a/scautable/src/csv.scala b/scautable/src/csv.scala
index 6604e29..294fd54 100644
--- a/scautable/src/csv.scala
+++ b/scautable/src/csv.scala
@@ -61,14 +61,14 @@ object CSV:
 
   // type Result = ReplaceOneType[InputTuple, EmptyTuple, "col1", Boolean]
 
-  type ReplaceOneTypeAtName[N <: Tuple, StrConst <: String, T <: Tuple, Head <: Tuple, A] <: Tuple = (T, N) match
+  type ReplaceOneTypeAtName[N <: Tuple, StrConst <: String, T <: Tuple, A] <: Tuple = (T, N) match
     case (EmptyTuple, _) => EmptyTuple
     case (_, EmptyTuple) => EmptyTuple
     case (nameHead *: nameTail, typeHead *: typeTail) =>
       IsMatch[nameHead, StrConst] match
           case true => A *: typeTail
           case false =>
-            typeHead *: ReplaceOneTypeAtName[nameTail, StrConst, typeTail, Head, A]
+            typeHead *: ReplaceOneTypeAtName[nameTail, StrConst, typeTail, A]
 
   // match
   //   case EmptyTuple => T *: A *: StrConst *:  EmptyTuple
@@ -153,9 +153,11 @@ object CSV:
           (fct(tup) *: tup.toTuple).withNames[Concat[S, K1]]
       }
 
+    inline def forceColumnType[S <: String, A] = {
+      itr.map(_.asInstanceOf[NamedTuple[K1, ReplaceOneTypeAtName[K1, S, V1, A]]])
+    }
 
-
-    inline def mapColumn[S <: String, B, A](fct: B => A)(using ev: IsColumn[S, K1] =:= true, s: ValueOf[S])= {
+    inline def mapColumn[S <: String, B, A](fct: B => A)(using ev: IsColumn[S, K1] =:= true, s: ValueOf[S]): Iterator[NamedTuple[K1, ReplaceOneTypeAtName[K1, S, V1, A]]]= {
       import scala.compiletime.ops.string.*
       val headers = constValueTuple[K1].toList.map(_.toString())
       type temp = "TEMP_COLUMN"
@@ -171,7 +173,7 @@ object CSV:
           val tup = x.toTuple
           val mapped = fct(tup(idx).asInstanceOf[B])
           val (head, tail) = x.toTuple.splitAt(idx)
-          (head ++ mapped *: tail.tail).withNames[K1].asInstanceOf[NamedTuple[K1,ReplaceOneTypeAtName[K1,  S, V1, EmptyTuple, A]]]
+          (head ++ mapped *: tail.tail).withNames[K1].asInstanceOf[NamedTuple[K1,ReplaceOneTypeAtName[K1,  S, V1, A]]]
       }
     }
 
diff --git a/scautable/test/jvm/src/testJvm.scala b/scautable/test/jvm/src/testJvm.scala
index 3295c57..393fb61 100644
--- a/scautable/test/jvm/src/testJvm.scala
+++ b/scautable/test/jvm/src/testJvm.scala
@@ -143,6 +143,16 @@ class CSVSuite extends munit.FunSuite:
     assertEquals(out.last.col2Renamed, "6")
   }
 
+  test("force column type") {
+    val csv: CsvIterator[("col1", "col2", "col3")] = CSV.absolutePath(Generated.resourceDir0 + "simple.csv")
+
+    val renamed: Iterator[(col1 : "col1", col2Renamed : String, col3 : "col3")]= csv.drop(1).renameColumn["col2", "col2Renamed"].forceColumnType["col2Renamed", String]
+    val out = renamed.toArray
+    assertEquals(out.head.col2Renamed, "2")
+    assertEquals(out.tail.head.col2Renamed, "4")
+    assertEquals(out.last.col2Renamed, "6")
+  }
+
   test("map column") {
     def csv = CSV.absolutePath(Generated.resourceDir0 + "simple.csv")
     def csvDrop1 = csv.drop(1)