diff --git a/tests/xtimer_now64_continuity/Makefile b/tests/xtimer_now64_continuity/Makefile
index 2902f849c95b628765976b1c869f65628cb2e2ca..7771d93310b5d2a27e04cef54ec7f4e614f7a397 100644
--- a/tests/xtimer_now64_continuity/Makefile
+++ b/tests/xtimer_now64_continuity/Makefile
@@ -3,6 +3,7 @@ include ../Makefile.tests_common
 USEMODULE += fmt
 USEMODULE += xtimer
 
-TEST_ON_CI_WHITELIST += all
+# This test randomly fails on `native` so disable it from CI
+TEST_ON_CI_WHITELIST += samr21-xpro
 
 include $(RIOTBASE)/Makefile.include
diff --git a/tests/xtimer_usleep/Makefile b/tests/xtimer_usleep/Makefile
index af26bcfb8f0b2a198000231dc250073ca61f5f30..a51966755eaf01b5dc46661c38e007e7657822e3 100644
--- a/tests/xtimer_usleep/Makefile
+++ b/tests/xtimer_usleep/Makefile
@@ -2,7 +2,8 @@ include ../Makefile.tests_common
 
 USEMODULE += xtimer
 
-TEST_ON_CI_WHITELIST += all
+# This test randomly fails on `native` so disable it from CI
+TEST_ON_CI_WHITELIST += samr21-xpro
 
 # Port and pin configuration for probing with oscilloscope
 # Port number should be found in port enum e.g in cpu/include/periph_cpu.h