diff --git a/src/_impl/_midpt_smooth_impl.scad b/src/_impl/_midpt_smooth_impl.scad
new file mode 100644
index 00000000..d5bd0e4d
--- /dev/null
+++ b/src/_impl/_midpt_smooth_impl.scad
@@ -0,0 +1,14 @@
+function _midpt_smooth_sub(points, iend, closed) = 
+    concat(
+        [
+            for(i = 0; i < iend; i = i + 1) 
+                (points[i] + points[i + 1]) / 2
+        ],
+        closed ? [(points[iend] + points[0]) / 2] : []
+    );
+
+function _midpt_smooth_impl(points, n, closed) =
+    let(
+        smoothed = _midpt_smooth_sub(points, len(points) - 1, closed)
+    )
+    n == 1 ? smoothed : _midpt_smooth_impl(smoothed, n - 1, closed);
\ No newline at end of file
diff --git a/src/midpt_smooth.scad b/src/midpt_smooth.scad
index ffefd922..8047d2c0 100644
--- a/src/midpt_smooth.scad
+++ b/src/midpt_smooth.scad
@@ -8,17 +8,6 @@
 *
 **/
 
-function _midpt_smooth_sub(points, iend, closed = false) = 
-    concat(
-        [
-            for(i = 0; i < iend; i = i + 1) 
-                (points[i] + points[i + 1]) / 2
-        ],
-        closed ? [(points[iend] + points[0]) / 2] : []
-    );
+use <_impl/_midpt_smooth_impl.scad>;
 
-function midpt_smooth(points, n, closed = false) =
-    let(
-        smoothed = _midpt_smooth_sub(points, len(points) - 1, closed)
-    )
-    n == 1 ? smoothed : midpt_smooth(smoothed, n - 1, closed);
\ No newline at end of file
+function midpt_smooth(points, n, closed = false) = _midpt_smooth_impl(points, n, closed);
\ No newline at end of file