diff --git a/test/unit/socket-close-test.ts b/test/unit/socket-close-test.ts
index 7a90c877..d26cbf2c 100644
--- a/test/unit/socket-close-test.ts
+++ b/test/unit/socket-close-test.ts
@@ -112,7 +112,7 @@ for (const proto of testProtos("tcp", "ipc", "inproc")) {
         }
         this.slow(200)
 
-        let weakRef
+        let weakRef: undefined | WeakRef<any>
 
         const task = async () => {
           let context: zmq.Context | undefined = new zmq.Context()
@@ -145,7 +145,7 @@ for (const proto of testProtos("tcp", "ipc", "inproc")) {
         }
         this.slow(200)
 
-        let weakRef
+        let weakRef: undefined | WeakRef<any>
         const task = async () => {
           let context: zmq.Context | undefined = new zmq.Context()
 
diff --git a/test/unit/socket-send-receive-test.ts b/test/unit/socket-send-receive-test.ts
index 8eee9c0f..a5855380 100644
--- a/test/unit/socket-send-receive-test.ts
+++ b/test/unit/socket-send-receive-test.ts
@@ -94,7 +94,7 @@ for (const proto of testProtos("tcp", "ipc", "inproc")) {
         if (process.env.SKIP_GC_TESTS) {
           this.skip()
         }
-        let weakRef
+        let weakRef: undefined | WeakRef<any>
         sockA.connect(uniqAddress(proto))
         const send = async (size: number) => {
           const msg = Buffer.alloc(size)
@@ -115,7 +115,7 @@ for (const proto of testProtos("tcp", "ipc", "inproc")) {
         if (process.env.SKIP_GC_TESTS) {
           this.skip()
         }
-        let weakRef
+        let weakRef: undefined | WeakRef<any>
 
         sockA.connect(uniqAddress(proto))
         const send = async (size: number) => {
@@ -130,7 +130,7 @@ for (const proto of testProtos("tcp", "ipc", "inproc")) {
           setTimeout(resolve, 5)
         })
         assert.isDefined(weakRef)
-        assert.isUndefined(weakRef!.unref())
+        assert.isUndefined(weakRef!.deref())
       })
     })