diff --git a/test/src/comp-test-funcs.el b/test/src/comp-test-funcs.el
index 1b0f3056b98..bcf9fcb0fd1 100644
--- a/test/src/comp-test-funcs.el
+++ b/test/src/comp-test-funcs.el
@@ -354,6 +354,22 @@
        comp-test-and-3-var
        2))
 
+(defun comp-test-copy-insn-f (insn)
+  ;; From `comp-copy-insn'.
+  (if (consp insn)
+      (let (result)
+	(while (consp insn)
+	  (let ((newcar (car insn)))
+	    (if (or (consp (car insn)) (comp-mvar-p (car insn)))
+		(setf newcar (comp-copy-insn (car insn))))
+	    (push newcar result))
+	  (setf insn (cdr insn)))
+	(nconc (nreverse result)
+               (if (comp-mvar-p insn) (comp-copy-insn insn) insn)))
+    (if (comp-mvar-p insn)
+        (copy-comp-mvar insn)
+      insn)))
+
 
 ;;;;;;;;;;;;;;;;;;;;
 ;; Tromey's tests ;;
diff --git a/test/src/comp-tests.el b/test/src/comp-tests.el
index 61838c670e1..b2f83998838 100644
--- a/test/src/comp-tests.el
+++ b/test/src/comp-tests.el
@@ -444,6 +444,11 @@ https://lists.gnu.org/archive/html/bug-gnu-emacs/2020-03/msg00914.html."
   (should (= (comp-test-and-3-f t) 2))
   (should (null (comp-test-and-3-f '(1 2)))))
 
+(comp-deftest copy-insn ()
+  (should (equal (comp-test-copy-insn-f '(1 2 3 (4 5 6)))
+                 '(1 2 3 (4 5 6))))
+  (should (null (comp-test-copy-insn-f nil))))
+
 
 ;;;;;;;;;;;;;;;;;;;;;
 ;; Tromey's tests. ;;