diff --git a/impls/cs/step8_macros.cs b/impls/cs/step8_macros.cs
index 9e111dd6..30e040be 100644
--- a/impls/cs/step8_macros.cs
+++ b/impls/cs/step8_macros.cs
@@ -162,6 +162,7 @@ namespace Mal {
                 a1 = ast[1];
                 a2 = ast[2];
                 res = EVAL(a2, env);
+                res = res.copy();
                 ((MalFunc)res).setMacro();
                 env.set(((MalSymbol)a1), res);
                 return res;
diff --git a/impls/cs/step9_try.cs b/impls/cs/step9_try.cs
index ba7b6dc9..31dab06c 100644
--- a/impls/cs/step9_try.cs
+++ b/impls/cs/step9_try.cs
@@ -162,6 +162,7 @@ namespace Mal {
                 a1 = ast[1];
                 a2 = ast[2];
                 res = EVAL(a2, env);
+                res = res.copy();
                 ((MalFunc)res).setMacro();
                 env.set(((MalSymbol)a1), res);
                 return res;
diff --git a/impls/cs/stepA_mal.cs b/impls/cs/stepA_mal.cs
index 56f3da09..cdc14901 100644
--- a/impls/cs/stepA_mal.cs
+++ b/impls/cs/stepA_mal.cs
@@ -162,6 +162,7 @@ namespace Mal {
                 a1 = ast[1];
                 a2 = ast[2];
                 res = EVAL(a2, env);
+                res = res.copy();
                 ((MalFunc)res).setMacro();
                 env.set(((MalSymbol)a1), res);
                 return res;