diff --git a/ext/polars/src/lib.rs b/ext/polars/src/lib.rs
index 774e0738c8..b6eda39807 100644
--- a/ext/polars/src/lib.rs
+++ b/ext/polars/src/lib.rs
@@ -48,25 +48,7 @@ type RbResult<T> = Result<T, Error>;
 #[magnus::init]
 fn init(ruby: &Ruby) -> RbResult<()> {
     let module = define_module("Polars")?;
-    module.define_singleton_method(
-        "_concat_lf_diagonal",
-        function!(functions::lazy::concat_lf_diagonal, 4),
-    )?;
     module.define_singleton_method("_rb_duration", function!(functions::lazy::duration, 9))?;
-    module.define_singleton_method("_concat_df", function!(functions::eager::concat_df, 1))?;
-    module.define_singleton_method("_concat_lf", function!(functions::lazy::concat_lf, 4))?;
-    module.define_singleton_method(
-        "_concat_df_diagonal",
-        function!(functions::eager::concat_df_diagonal, 1),
-    )?;
-    module.define_singleton_method(
-        "_concat_df_horizontal",
-        function!(functions::eager::concat_df_horizontal, 1),
-    )?;
-    module.define_singleton_method(
-        "_concat_series",
-        function!(functions::eager::concat_series, 1),
-    )?;
     module.define_singleton_method("_ipc_schema", function!(functions::io::read_ipc_schema, 1))?;
     module.define_singleton_method(
         "_parquet_schema",
@@ -643,6 +625,24 @@ fn init(ruby: &Ruby) -> RbResult<()> {
     class.define_singleton_method("as_struct", function!(functions::lazy::as_struct, 1))?;
     class.define_singleton_method("coalesce_exprs", function!(functions::lazy::coalesce, 1))?;
     class.define_singleton_method("arg_where", function!(functions::lazy::arg_where, 1))?;
+    class.define_singleton_method(
+        "concat_lf_diagonal",
+        function!(functions::lazy::concat_lf_diagonal, 4),
+    )?;
+    class.define_singleton_method("concat_df", function!(functions::eager::concat_df, 1))?;
+    class.define_singleton_method("concat_lf", function!(functions::lazy::concat_lf, 4))?;
+    class.define_singleton_method(
+        "concat_df_diagonal",
+        function!(functions::eager::concat_df_diagonal, 1),
+    )?;
+    class.define_singleton_method(
+        "concat_df_horizontal",
+        function!(functions::eager::concat_df_horizontal, 1),
+    )?;
+    class.define_singleton_method(
+        "concat_series",
+        function!(functions::eager::concat_series, 1),
+    )?;
 
     let class = module.define_class("RbLazyFrame", ruby.class_object())?;
     class.define_singleton_method("read_json", function!(RbLazyFrame::read_json, 1))?;
diff --git a/lib/polars/functions.rb b/lib/polars/functions.rb
index 522256495f..f8b4690a99 100644
--- a/lib/polars/functions.rb
+++ b/lib/polars/functions.rb
@@ -53,27 +53,27 @@ def concat(items, rechunk: true, how: "vertical", parallel: true)
       first = items[0]
       if first.is_a?(DataFrame)
         if how == "vertical"
-          out = Utils.wrap_df(_concat_df(items))
+          out = Utils.wrap_df(Plr.concat_df(items))
         elsif how == "diagonal"
-          out = Utils.wrap_df(_concat_df_diagonal(items))
+          out = Utils.wrap_df(Plr.concat_df_diagonal(items))
         elsif how == "horizontal"
-          out = Utils.wrap_df(_concat_df_horizontal(items))
+          out = Utils.wrap_df(Plr.concat_df_horizontal(items))
         else
           raise ArgumentError, "how must be one of {{'vertical', 'diagonal', 'horizontal'}}, got #{how}"
         end
       elsif first.is_a?(LazyFrame)
         if how == "vertical"
-          return Utils.wrap_ldf(_concat_lf(items, rechunk, parallel, false))
+          return Utils.wrap_ldf(Plr.concat_lf(items, rechunk, parallel, false))
         elsif how == "vertical_relaxed"
-          return Utils.wrap_ldf(_concat_lf(items, rechunk, parallel, true))
+          return Utils.wrap_ldf(Plr.concat_lf(items, rechunk, parallel, true))
         elsif how == "diagonal"
-          return Utils.wrap_ldf(_concat_lf_diagonal(items, rechunk, parallel, false))
+          return Utils.wrap_ldf(Plr.concat_lf_diagonal(items, rechunk, parallel, false))
         else
           raise ArgumentError, "Lazy only allows 'vertical', 'vertical_relaxed', and 'diagonal' concat strategy."
         end
       elsif first.is_a?(Series)
         # TODO
-        out = Utils.wrap_s(_concat_series(items))
+        out = Utils.wrap_s(Plr.concat_series(items))
       elsif first.is_a?(Expr)
         out = first
         items[1..-1].each do |e|