diff --git a/repos/os/src/test/timeout/main.cc b/repos/os/src/test/timeout/main.cc
index 5505979350..4bedbab118 100644
--- a/repos/os/src/test/timeout/main.cc
+++ b/repos/os/src/test/timeout/main.cc
@@ -18,6 +18,7 @@
 #include <util/fifo.h>
 #include <util/misc_math.h>
 #include <base/attached_rom_dataspace.h>
+#include <cpu/memory_barrier.h>
 
 using namespace Genode;
 
@@ -521,7 +522,7 @@ struct Fast_polling : Test
 
 			/* measure consumed time of a limited busy loop */
 			uint64_t volatile start_ms = timer_2.elapsed_ms();
-			for (unsigned long volatile cnt = 0; cnt < max_cnt; cnt++) { }
+			for (unsigned long cnt = 0; cnt < max_cnt; cnt++) memory_barrier();
 			uint64_t volatile end_ms = timer_2.elapsed_ms();
 
 			/*
@@ -568,10 +569,11 @@ struct Fast_polling : Test
 			for (unsigned poll = 0; poll < nr_of_polls; poll++) {
 
 				/* create delay between two polls */
-				for (unsigned long volatile i = 0; i < delay_loops_per_poll_; i++) { }
+				for (unsigned long i = 0; i < delay_loops_per_poll_; i++)
+					memory_barrier();
 
 				/* count delay loops to limit frequency of remote time reading */
-				delay_loops += delay_loops_per_poll_;
+				delay_loops = delay_loops + delay_loops_per_poll_;
 
 				/*
 				 * We buffer the results in local variables first so the RAM
@@ -646,10 +648,13 @@ struct Fast_polling : Test
 				} else {
 
 					if (timer_2_delayed) {
-						local_us_1_buf.value[poll] += timer_diff_us;
-						local_us_2_buf.value[poll] += timer_diff_us;
+						local_us_1_buf.value[poll] =
+							local_us_1_buf.value[poll] + timer_diff_us;
+						local_us_2_buf.value[poll] =
+							local_us_2_buf.value[poll] + timer_diff_us;
 					} else {
-						remote_us_buf.value[poll] += timer_diff_us;
+						remote_us_buf.value[poll] =
+							remote_us_buf.value[poll] + timer_diff_us;
 					}
 					nr_of_good_polls++;
 				}