diff --git a/src/ucp/core/ucp_request.inl b/src/ucp/core/ucp_request.inl
index 386dc68fd665..77102b6548d0 100644
--- a/src/ucp/core/ucp_request.inl
+++ b/src/ucp/core/ucp_request.inl
@@ -64,12 +64,15 @@
 
 #define ucp_request_complete(_req, _cb, _status, ...) \
     { \
+        /* NOTE: external request can't have RELEASE flag and we */ \
+        /* will never put it into mpool */ \
+        uint32_t _released = ((_req)->flags |= UCP_REQUEST_FLAG_COMPLETED) & \
+                             UCP_REQUEST_FLAG_RELEASED; \
         (_req)->status = (_status); \
         if (ucs_likely((_req)->flags & UCP_REQUEST_FLAG_CALLBACK)) { \
             (_req)->_cb((_req) + 1, (_status), ## __VA_ARGS__); \
         } \
-        if (ucs_unlikely(((_req)->flags  |= UCP_REQUEST_FLAG_COMPLETED) & \
-                         UCP_REQUEST_FLAG_RELEASED)) { \
+        if (ucs_unlikely(_released)) { \
             ucp_request_put(_req); \
         } \
     }
diff --git a/test/gtest/ucp/test_ucp_tag.cc b/test/gtest/ucp/test_ucp_tag.cc
index eaf0dd2ffc93..1440126b77ed 100644
--- a/test/gtest/ucp/test_ucp_tag.cc
+++ b/test/gtest/ucp/test_ucp_tag.cc
@@ -14,6 +14,7 @@ extern "C" {
 #include <ucp/core/ucp_worker.h>
 #include <ucp/core/ucp_ep.h>
 #include <ucp/core/ucp_ep.inl>
+#include <ucs/arch/atomic.h>
 }
 
 #include <sys/mman.h>
@@ -462,28 +463,39 @@ UCS_TEST_P(test_ucp_tag_limits, check_max_short_zcopy_thresh_zero, "ZCOPY_THRESH
 UCP_INSTANTIATE_TEST_CASE(test_ucp_tag_limits)
 
 
-class test_ucp_tag_fallback : public ucp_test {
+class test_ucp_tag_nbx : public test_ucp_tag {
 public:
     void init() {
         /* forbid zcopy access because it will always fail due to read-only
          * memory pages (will fail to register memory) */
         modify_config("ZCOPY_THRESH", "inf");
-        ucp_test::init();
-        sender().connect(&receiver(), get_ep_params());
-        receiver().connect(&sender(), get_ep_params());
-    }
-
-    static void get_test_variants(std::vector<ucp_test_variant>& variants) {
-        add_variant(variants, UCP_FEATURE_TAG);
+        test_ucp_tag::init();
+        m_completed = 0;
     }
 
 protected:
     static const size_t MSG_SIZE;
+    uint32_t m_completed;
+
+    static void send_callback(void *req, ucs_status_t status,
+                              void *user_data)
+    {
+        request_free((request*)req);
+        ucs_atomic_add32((volatile uint32_t*)user_data, 1);
+    }
+
+    static void recv_callback(void *req, ucs_status_t status,
+                              const ucp_tag_recv_info_t *info,
+                              void *user_data)
+    {
+        request_free((request*)req);
+        ucs_atomic_add32((volatile uint32_t*)user_data, 1);
+    }
 };
 
-const size_t test_ucp_tag_fallback::MSG_SIZE  = 4 * 1024 * ucs_get_page_size();
+const size_t test_ucp_tag_nbx::MSG_SIZE  = 4 * UCS_KBYTE * ucs_get_page_size();
 
-UCS_TEST_P(test_ucp_tag_fallback, fallback)
+UCS_TEST_P(test_ucp_tag_nbx, fallback)
 {
     ucp_request_param_t param = {0};
 
@@ -509,4 +521,35 @@ UCS_TEST_P(test_ucp_tag_fallback, fallback)
     munmap(send_buffer, MSG_SIZE);
 }
 
-UCP_INSTANTIATE_TEST_CASE(test_ucp_tag_fallback)
+UCS_TEST_P(test_ucp_tag_nbx, external_request_free)
+{
+    ucp_request_param_t send_param;
+    ucp_request_param_t recv_param;
+
+    send_param.op_attr_mask = recv_param.op_attr_mask = UCP_OP_ATTR_FIELD_CALLBACK |
+                                                        UCP_OP_ATTR_FIELD_REQUEST  |
+                                                        UCP_OP_ATTR_FLAG_NO_IMM_CMPL |
+                                                        UCP_OP_ATTR_FIELD_USER_DATA;
+    send_param.user_data   = recv_param.user_data     = &m_completed;
+    send_param.request     = request_alloc();
+    recv_param.request     = request_alloc();
+    send_param.cb.send     = (ucp_send_nbx_callback_t)send_callback;
+    recv_param.cb.recv     = (ucp_tag_recv_nbx_callback_t)recv_callback;
+    send_param.user_data   = &m_completed;
+    recv_param.user_data   = &m_completed;
+
+    std::vector<char> send_buffer(MSG_SIZE);
+    std::vector<char> recv_buffer(MSG_SIZE);
+
+    ucs_status_ptr_t recv_req = ucp_tag_recv_nbx(receiver().worker(),
+                                                 &recv_buffer[0], MSG_SIZE,
+                                                 0, 0, &recv_param);
+    ASSERT_TRUE(UCS_PTR_IS_PTR(recv_req));
+    ucs_status_ptr_t send_req = ucp_tag_send_nbx(sender().ep(), &send_buffer[0],
+                                                 MSG_SIZE, 0, &send_param);
+    ASSERT_TRUE(UCS_PTR_IS_PTR(send_req));
+
+    wait_for_value(&m_completed, 2u);
+}
+
+UCP_INSTANTIATE_TEST_CASE(test_ucp_tag_nbx)
diff --git a/test/gtest/ucp/ucp_test.h b/test/gtest/ucp/ucp_test.h
index 36f0f4811fc2..a5c93ff1656c 100644
--- a/test/gtest/ucp/ucp_test.h
+++ b/test/gtest/ucp/ucp_test.h
@@ -297,6 +297,15 @@ class ucp_test : public ucp_test_base,
         }
     }
 
+    template <typename T>
+    void wait_for_value(volatile T *var, T value, double timeout = 10.0) const
+    {
+        ucs_time_t deadline = ucs_get_time() +
+                              ucs_time_from_sec(timeout) * ucs::test_time_multiplier();
+        while ((ucs_get_time() < deadline) && (*var != value)) {
+            short_progress_loop();
+        }
+    }
     static const ucp_datatype_t DATATYPE;
     static const ucp_datatype_t DATATYPE_IOV;