diff --git a/test/client/test_client.py b/test/client/test_client.py
index 857e498..f7a59cd 100755
--- a/test/client/test_client.py
+++ b/test/client/test_client.py
@@ -293,3 +293,78 @@ def _test_suppress_positive_response_wait_nrc_case5(self):
         with self.udsclient.suppress_positive_response(wait_nrc=True):
             resp = self.udsclient.tester_present()
             self.assertIsNotNone(resp)
+
+    def test_pending_positive_response(self):
+        self.conn.touserqueue.get(timeout=0.2)
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7E\x00")
+
+    def _test_pending_positive_response(self):
+        req = Request(service=services.TesterPresent, subfunction=0)
+        resp = self.udsclient.send_request(req)
+        self.assertEqual(resp.original_payload, b'\x7E\x00')
+        self.assertEqual(self.udsclient.response_pending_times, 1)
+
+    def test_pending_negative_response(self):
+        self.conn.touserqueue.get(timeout=0.2)
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x22")
+
+    def _test_pending_negative_response(self):
+        req = Request(service=services.TesterPresent, subfunction=0)
+        with self.assertRaises(NegativeResponseException):
+            self.udsclient.send_request(req)
+        self.assertEqual(self.udsclient.response_pending_times, 1)
+
+    def test_suppress_positive_response_pending_case1(self):
+        self.conn.touserqueue.get(timeout=0.2)
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7E\x00")
+
+    def _test_suppress_positive_response_pending_case1(self):
+        # Case 3 - Negative and wait
+        req = Request(service=services.TesterPresent, subfunction=0)
+        with self.udsclient.suppress_positive_response(wait_nrc=True):
+            resp = self.udsclient.send_request(req)
+            self.assertEqual(resp.original_payload, b'\x7E\x00')
+            self.assertEqual(self.udsclient.response_pending_times, 1)
+
+    def test_suppress_positive_response_response_pending_case2(self):
+        self.conn.touserqueue.get(timeout=0.2)
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x31")
+
+    def _test_suppress_positive_response_response_pending_case2(self):
+        req = Request(service=services.TesterPresent, subfunction=0)
+        with self.assertRaises(NegativeResponseException):
+            with self.udsclient.suppress_positive_response(wait_nrc=True):
+                self.udsclient.send_request(req)
+            self.assertEqual(self.udsclient.response_pending_times, 1)
+
+    def test_suppress_positive_response_response_pending_case3(self):
+        self.conn.touserqueue.get(timeout=0.2)
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x31")
+
+    def _test_suppress_positive_response_response_pending_case3(self):
+        # Case 3 - Negative and wait
+        req = Request(service=services.TesterPresent, subfunction=0)
+        with self.assertRaises(NegativeResponseException) as exc:
+            with self.udsclient.suppress_positive_response(wait_nrc=True):
+                self.udsclient.send_request(req)
+            self.assertEqual(self.udsclient.response_pending_times, 3)
+
+    def test_suppress_positive_response_response_pending_negative_case1(self):
+        self.conn.touserqueue.get(timeout=0.2)
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x78")
+        self.conn.fromuserqueue.put(b"\x7F\x3E\x31")
+
+    def _test_suppress_positive_response_response_pending_negative_case1(self):
+        req = Request(service=services.TesterPresent, subfunction=0)
+        with self.assertRaises(NegativeResponseException):
+            with self.udsclient.suppress_positive_response(wait_nrc=True):
+                self.udsclient.send_request(req)
+            self.assertEqual(self.udsclient.response_pending_times, 2)
\ No newline at end of file
diff --git a/udsoncan/client.py b/udsoncan/client.py
index 685f9cd..a9ebeeb 100755
--- a/udsoncan/client.py
+++ b/udsoncan/client.py
@@ -110,6 +110,7 @@ def __init__(self, conn: BaseConnection, config: ClientConfig = default_client_c
         self.suppress_positive_response = Client.SuppressPositiveResponse()
         self.payload_override = Client.PayloadOverrider()
         self.last_response = None
+        self.response_pending_times = 0
 
         self.session_timing = cast(SessionTiming, dict(p2_server_max=None, p2_star_server_max=None))    # python 3.7 cast
 
@@ -2247,6 +2248,7 @@ def send_request(self, request: Request, timeout: int = -1) -> Optional[Response
 
                 if response.code == Response.Code.RequestCorrectlyReceived_ResponsePending:
                     done_receiving = False
+                    self.response_pending_times += 1
                     if not using_p2_star:
                         # Received a 0x78 NRC: timeout is now set to P2*
                         p2_star = self.config['p2_star_timeout'] if self.session_timing['p2_star_server_max'] is None else self.session_timing['p2_star_server_max']
@@ -2263,7 +2265,7 @@ def send_request(self, request: Request, timeout: int = -1) -> Optional[Response
 
         response.original_request = request
 
-        if spr_used:
+        if spr_used and self.response_pending_times == 0:
             return None
 
         return response