diff --git a/distributors.scad b/distributors.scad
index ff3482e..026dc72 100644
--- a/distributors.scad
+++ b/distributors.scad
@@ -171,7 +171,11 @@ module line_of(spacing, n, l, p1, p2)
 module xcopies(spacing, n, l, sp)
 {
     sp = is_finite(sp)? [sp,0,0] : sp;
-    line_of(l=l*RIGHT, spacing=spacing*RIGHT, n=n, p1=sp) children();
+    line_of(
+        l=u_mul(l,RIGHT),
+        spacing=u_mul(spacing,RIGHT),
+        n=n, p1=sp
+    ) children();
 }
 
 
@@ -207,7 +211,11 @@ module xcopies(spacing, n, l, sp)
 module ycopies(spacing, n, l, sp)
 {
     sp = is_finite(sp)? [0,sp,0] : sp;
-    line_of(l=l*BACK, spacing=spacing*BACK, n=n, p1=sp) children();
+    line_of(
+        l=u_mul(l,BACK),
+        spacing=u_mul(spacing,BACK),
+        n=n, p1=sp
+    ) children();
 }
 
 
@@ -243,7 +251,11 @@ module ycopies(spacing, n, l, sp)
 module zcopies(spacing, n, l, sp)
 {
     sp = is_finite(sp)? [0,0,sp] : sp;
-    line_of(l=l*UP, spacing=spacing*UP, n=n, p1=sp) children();
+    line_of(
+        l=u_mul(l,UP),
+        spacing=u_mul(spacing,UP),
+        n=n, p1=sp
+    ) children();
 }
 
 
diff --git a/math.scad b/math.scad
index 6cb1362..a2b811d 100644
--- a/math.scad
+++ b/math.scad
@@ -169,6 +169,63 @@ function lerp(a,b,u) =
 
 
 
+// Section: Undef Safe Math
+
+// Function: u_add()
+// Usage:
+//   x = u_add(a, b);
+// Description:
+//   Adds `a` to `b`, returning the result, or undef if either value is `undef`.
+//   This emulates the way undefs used to be handled in versions of OpenSCAD before 2020.
+// Arguments:
+//   a = First value.
+//   b = Second value.
+function u_add(a,b) = is_undef(a) || is_undef(b)? undef : a + b;
+
+
+// Function: u_sub()
+// Usage:
+//   x = u_sub(a, b);
+// Description:
+//   Subtracts `b` from `a`, returning the result, or undef if either value is `undef`.
+//   This emulates the way undefs used to be handled in versions of OpenSCAD before 2020.
+// Arguments:
+//   a = First value.
+//   b = Second value.
+function u_sub(a,b) = is_undef(a) || is_undef(b)? undef : a - b;
+
+
+// Function: u_mul()
+// Usage:
+//   x = u_mul(a, b);
+// Description:
+//   Multiplies `a` by `b`, returning the result, or undef if either value is `undef`.
+//   This emulates the way undefs used to be handled in versions of OpenSCAD before 2020.
+// Arguments:
+//   a = First value.
+//   b = Second value.
+function u_mul(a,b) =
+    is_undef(a) || is_undef(b)? undef :
+    is_vector(a) && is_vector(b)? vmul(a,b) :
+    a * b;
+
+
+// Function: u_div()
+// Usage:
+//   x = u_div(a, b);
+// Description:
+//   Divides `a` by `b`, returning the result, or undef if either value is `undef`.
+//   This emulates the way undefs used to be handled in versions of OpenSCAD before 2020.
+// Arguments:
+//   a = First value.
+//   b = Second value.
+function u_div(a,b) =
+    is_undef(a) || is_undef(b)? undef :
+    is_vector(a) && is_vector(b)? vdiv(a,b) :
+    a / b;
+
+
+
 // Section: Hyperbolic Trigonometry
 
 // Function: sinh()
diff --git a/tests/test_math.scad b/tests/test_math.scad
index 56f3ae2..2103eb8 100644
--- a/tests/test_math.scad
+++ b/tests/test_math.scad
@@ -382,6 +382,74 @@ module test_lerp() {
 test_lerp();
 
 
+module test_u_add() {
+    assert_equal(u_add(1,2),3);
+    assert_equal(u_add(1,-2),-1);
+    assert_equal(u_add(-1,2),1);
+    assert_equal(u_add(-1,-2),-3);
+    assert_equal(u_add(243,-27),216);
+    assert_equal(u_add([2,3,4],[8,7,9]),[10,10,13]);
+    assert_equal(u_add(undef,27),undef);
+    assert_equal(u_add(undef,-27),undef);
+    assert_equal(u_add(243,undef),undef);
+    assert_equal(u_add(-43,undef),undef);
+    assert_equal(u_add(undef,[8,7,9]),undef);
+    assert_equal(u_add([2,3,4],undef),undef);
+}
+test_u_add();
+
+
+module test_u_sub() {
+    assert_equal(u_sub(1,2),-1);
+    assert_equal(u_sub(1,-2),3);
+    assert_equal(u_sub(-1,2),-3);
+    assert_equal(u_sub(-1,-2),1);
+    assert_equal(u_sub(243,-27),270);
+    assert_equal(u_sub([2,3,4],[8,7,9]),[-6,-4,-5]);
+    assert_equal(u_sub(undef,27),undef);
+    assert_equal(u_sub(undef,-27),undef);
+    assert_equal(u_sub(243,undef),undef);
+    assert_equal(u_sub(-43,undef),undef);
+    assert_equal(u_sub(undef,[8,7,9]),undef);
+    assert_equal(u_sub([2,3,4],undef),undef);
+}
+test_u_sub();
+
+
+module test_u_mul() {
+    assert_equal(u_mul(3,2),6);
+    assert_equal(u_mul(3,-2),-6);
+    assert_equal(u_mul(-3,2),-6);
+    assert_equal(u_mul(-3,-2),6);
+    assert_equal(u_mul(243,-27),-6561);
+    assert_equal(u_mul([2,3,4],[8,7,9]),[16,21,36]);
+    assert_equal(u_mul(undef,27),undef);
+    assert_equal(u_mul(undef,-27),undef);
+    assert_equal(u_mul(243,undef),undef);
+    assert_equal(u_mul(-43,undef),undef);
+    assert_equal(u_mul(undef,[8,7,9]),undef);
+    assert_equal(u_mul([2,3,4],undef),undef);
+}
+test_u_mul();
+
+
+module test_u_div() {
+    assert_equal(u_div(1,2),1/2);
+    assert_equal(u_div(1,-2),-1/2);
+    assert_equal(u_div(-1,2),-1/2);
+    assert_equal(u_div(-1,-2),1/2);
+    assert_equal(u_div(243,-27),-9);
+    assert_equal(u_div([8,7,9],[2,3,4]),[4,7/3,9/4]);
+    assert_equal(u_div(undef,27),undef);
+    assert_equal(u_div(undef,-27),undef);
+    assert_equal(u_div(243,undef),undef);
+    assert_equal(u_div(-43,undef),undef);
+    assert_equal(u_div(undef,[8,7,9]),undef);
+    assert_equal(u_div([2,3,4],undef),undef);
+}
+test_u_div();
+
+
 module test_hypot() {
     assert_approx(hypot(20,30), norm([20,30]));
 }
diff --git a/version.scad b/version.scad
index dfc5f4f..37c60db 100644
--- a/version.scad
+++ b/version.scad
@@ -8,7 +8,7 @@
 //////////////////////////////////////////////////////////////////////
 
 
-BOSL_VERSION = [2,0,474];
+BOSL_VERSION = [2,0,475];
 
 
 // Section: BOSL Library Version Functions