diff --git a/tests/http/clients/ws-data.c b/tests/http/clients/ws-data.c
index 6698326dfb..4a3be67bf2 100644
--- a/tests/http/clients/ws-data.c
+++ b/tests/http/clients/ws-data.c
@@ -103,6 +103,9 @@ static CURLcode send_binary(CURL *curl, char *buf, size_t buflen)
   return result;
 }
 
+#if defined(__TANDEM)
+# include <cextdecs.h(PROCESS_DELAY_)>
+#endif
 static CURLcode recv_binary(CURL *curl, char *exp_data, size_t exp_len)
 {
   const struct curl_ws_frame *frame;
@@ -118,6 +121,13 @@ static CURLcode recv_binary(CURL *curl, char *exp_data, size_t exp_len)
       fprintf(stderr, "EAGAIN, sleep, try again\n");
 #ifdef _WIN32
       Sleep(100);
+#elif defined(__TANDEM)
+      /* NonStop only defines usleep when building for a threading model */
+# if defined(_PUT_MODEL_) || defined(_KLT_MODEL_)
+      usleep(100*1000);
+# else
+      PROCESS_DELAY_(100*1000);
+# endif
 #else
       usleep(100*1000);
 #endif
diff --git a/tests/http/clients/ws-pingpong.c b/tests/http/clients/ws-pingpong.c
index efb01bcd71..f11d217f47 100644
--- a/tests/http/clients/ws-pingpong.c
+++ b/tests/http/clients/ws-pingpong.c
@@ -94,6 +94,9 @@ static void websocket_close(CURL *curl)
           "ws: curl_ws_send returned %u, sent %u\n", (int)result, (int)sent);
 }
 
+#if defined(__TANDEM)
+# include <cextdecs.h(PROCESS_DELAY_)>
+#endif
 static CURLcode pingpong(CURL *curl, const char *payload)
 {
   CURLcode res;
@@ -108,6 +111,13 @@ static CURLcode pingpong(CURL *curl, const char *payload)
     if(res == CURLE_AGAIN) {
 #ifdef _WIN32
       Sleep(100);
+#elif defined(__TANDEM)
+      /* NonStop only defines usleep when building for a threading model */
+# if defined(_PUT_MODEL_) || defined(_KLT_MODEL_)
+      usleep(100*1000);
+# else
+      PROCESS_DELAY_(100*1000);
+# endif
 #else
       usleep(100*1000);
 #endif