diff --git a/src/__private__/_m_multiply.scad b/src/__private__/_m_multiply.scad
new file mode 100644
index 00000000..cb05476e
--- /dev/null
+++ b/src/__private__/_m_multiply.scad
@@ -0,0 +1,13 @@
+function _m_multiply(ma, mb) = 
+    let(
+        c1 = [mb[0][0], mb[1][0], mb[2][0], mb[3][0]],
+        c2 = [mb[0][1], mb[1][1], mb[2][1], mb[3][1]],
+        c3 = [mb[0][2], mb[1][2], mb[2][2], mb[3][2]],
+        c4 = [mb[0][3], mb[1][3], mb[2][3], mb[3][3]]
+    )
+    [
+        [ma[0] * c1, ma[0] * c2, ma[0] * c3, ma[0] * c4],
+        [ma[1] * c1, ma[1] * c2, ma[1] * c3, ma[1] * c4],
+        [ma[2] * c1, ma[2] * c2, ma[2] * c3, ma[2] * c4],
+        [ma[3] * c1, ma[3] * c2, ma[3] * c3, ma[3] * c4]
+    ];
\ No newline at end of file
diff --git a/src/m_multiply.scad b/src/m_multiply.scad
index fb6f8da1..a6306ac4 100644
--- a/src/m_multiply.scad
+++ b/src/m_multiply.scad
@@ -1,13 +1,3 @@
-function m_multiply(ma, mb) = 
-    let(
-        c1 = [mb[0][0], mb[1][0], mb[2][0], mb[3][0]],
-        c2 = [mb[0][1], mb[1][1], mb[2][1], mb[3][1]],
-        c3 = [mb[0][2], mb[1][2], mb[2][2], mb[3][2]],
-        c4 = [mb[0][3], mb[1][3], mb[2][3], mb[3][3]]
-    )
-    [
-        [ma[0] * c1, ma[0] * c2, ma[0] * c3, ma[0] * c4],
-        [ma[1] * c1, ma[1] * c2, ma[1] * c3, ma[1] * c4],
-        [ma[2] * c1, ma[2] * c2, ma[2] * c3, ma[2] * c4],
-        [ma[3] * c1, ma[3] * c2, ma[3] * c3, ma[3] * c4]
-    ];
\ No newline at end of file
+include <__private__/_m_multiply.scad>;
+
+function m_multiply(ma, mb) = _m_multiply(ma, mb);
\ No newline at end of file