diff --git a/package.json b/package.json
index c9ad113..7d3821c 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "memoredis",
-  "version": "1.0.1",
+  "version": "1.0.2",
   "description": "Redis memoization library with good Typescript generics, locking, and argument-wide bulk invalidation",
   "main": "build/main/index.js",
   "typings": "build/main/index.d.ts",
diff --git a/src/lib/memoizer.spec.ts b/src/lib/memoizer.spec.ts
index e9595b9..7d6ed3b 100644
--- a/src/lib/memoizer.spec.ts
+++ b/src/lib/memoizer.spec.ts
@@ -175,3 +175,30 @@ describe('invalidation', () => {
     expect(mock).toHaveBeenCalledTimes(1);
   });
 });
+
+describe('prefixes', () => {
+  test('should keep keyspaces separate', async () => {
+    const a = createMemoizer({ prefix: 'a' });
+    const b = createMemoizer({ prefix: 'b' });
+
+    const mock = jest.fn();
+
+    const memoizableFunction = async () => {
+      mock();
+      return 4;
+    };
+
+    const aF = a.memoize(memoizableFunction, {
+      key: 'prefix-test'
+    });
+
+    const bF = b.memoize(memoizableFunction, {
+      key: 'prefix-test'
+    });
+
+    await aF({ a: 1 });
+    await bF({ a: 1 });
+
+    expect(mock).toHaveBeenCalledTimes(2);
+  });
+});
diff --git a/src/lib/memoizer.ts b/src/lib/memoizer.ts
index 2b9437a..b61908c 100644
--- a/src/lib/memoizer.ts
+++ b/src/lib/memoizer.ts
@@ -54,7 +54,7 @@ export const createMemoizer = (instanceOpts: MemoizerOpts) => {
       client.get(key, (err, reply) =>
         err
           ? reject(err)
-          : resolve(reply === null ? (JSON.parse(reply) as T) : (reply as null))
+          : resolve(reply !== null ? (JSON.parse(reply) as T) : (reply as null))
       )
     );