diff --git a/addon-test-support/@ember/test-helpers/setup-context.ts b/addon-test-support/@ember/test-helpers/setup-context.ts
index 5ff4c5d1b..87e88ac40 100644
--- a/addon-test-support/@ember/test-helpers/setup-context.ts
+++ b/addon-test-support/@ember/test-helpers/setup-context.ts
@@ -464,14 +464,20 @@ export default function setupContext<T extends object>(
                 'You cannot call `this.setProperties` when passing a component to `render()` (the rendered component does not have access to the test context)'
               );
             } else {
-              let setCalls = SetUsage.get(context);
-
-              if (SetUsage.get(context) === undefined) {
-                setCalls = [];
-                SetUsage.set(context, setCalls);
+              // While neither the types nor the API documentation indicate that passing `null` or
+              // `undefined` to `setProperties` is allowed, it works and *has worked* for a long
+              // time, so there is considerable real-world code which relies on the fact that it
+              // does in fact work. Checking and no-op-ing here handles that.
+              if (hash != null) {
+                let setCalls = SetUsage.get(context);
+
+                if (SetUsage.get(context) === undefined) {
+                  setCalls = [];
+                  SetUsage.set(context, setCalls);
+                }
+
+                setCalls?.push(...Object.keys(hash));
               }
-
-              setCalls?.push(...Object.keys(hash));
             }
             return setProperties(context, hash);
           });
diff --git a/tests/unit/setup-context-test.js b/tests/unit/setup-context-test.js
index 291756029..76f05bab1 100644
--- a/tests/unit/setup-context-test.js
+++ b/tests/unit/setup-context-test.js
@@ -116,6 +116,28 @@ module('setupContext', function (hooks) {
         );
       });
 
+      test('this.setProperties handles `null` and `undefined` (back-compat only!)', function (assert) {
+        assert.expect(3);
+
+        context.setProperties();
+        assert.ok(
+          true,
+          'this.setProperties works with no args (for back-compat only)'
+        );
+
+        context.setProperties(null);
+        assert.ok(
+          true,
+          'this.setProperties works with `null` (for back-compat only)'
+        );
+
+        context.setProperties(undefined);
+        assert.ok(
+          true,
+          'this.setProperties works with `undefined` (for back-compat only)'
+        );
+      });
+
       test('it sets up this.get', function (assert) {
         context.set('foo', 'bar');