diff --git a/cpu/kinetis/include/periph_cpu.h b/cpu/kinetis/include/periph_cpu.h
index 7b81bb9c35..6cec6d6c23 100644
--- a/cpu/kinetis/include/periph_cpu.h
+++ b/cpu/kinetis/include/periph_cpu.h
@@ -500,7 +500,7 @@ enum {
 #ifndef RTT_FREQUENCY
 #define RTT_FREQUENCY       RTT_MAX_FREQUENCY
 #endif
-#if IS_USED(PERIPH_RTT)
+#if IS_USED(MODULE_PERIPH_RTT)
 /* On kinetis periph_rtt is built on top on an LPTIMER so if used it
    will conflict with xtimer, if a LPTIMER backend and RTT are needed
    consider using ztimer */
diff --git a/cpu/kinetis/periph/rtt.c b/cpu/kinetis/periph/rtt.c
index 59079f2a38..d7f57ce9a0 100644
--- a/cpu/kinetis/periph/rtt.c
+++ b/cpu/kinetis/periph/rtt.c
@@ -31,7 +31,7 @@
 #include "debug.h"
 
 static rtt_cb_t alarm_cb = NULL;       /**< callback called from RTC alarm */
-static void *alarm_arg;                /**< argument passed to the callback */
+static void *alarm_arg = NULL;         /**< argument passed to the callback */
 static uint32_t alarm_value = 0;
 
 static void _rtt_cb(void *arg, int channel)
@@ -46,7 +46,6 @@ static void _rtt_cb(void *arg, int channel)
 void rtt_init(void)
 {
     timer_init(RTT_DEV, RTT_FREQUENCY, _rtt_cb, NULL);
-    alarm_value = 0;
 }
 
 uint32_t rtt_get_counter(void)
@@ -60,7 +59,7 @@ void rtt_set_alarm(uint32_t alarm, rtt_cb_t cb, void *arg)
     alarm_arg = arg;
     alarm_cb = cb;
     alarm_value = alarm;
-    timer_set_absolute(RTT_DEV, 0, alarm % RTT_MAX_VALUE);
+    timer_set_absolute(RTT_DEV, 0, alarm & RTT_MAX_VALUE);
     irq_restore(state);
 }
 
@@ -71,7 +70,11 @@ uint32_t rtt_get_alarm(void)
 
 void rtt_clear_alarm(void)
 {
+    unsigned state = irq_disable();
+    alarm_cb = NULL;
+    alarm_arg = NULL;
     timer_clear(RTT_DEV, 0);
+    irq_restore(state);
 }
 
 void rtt_poweron(void)
diff --git a/tests/periph_rtt_min/Makefile b/tests/periph_rtt_min/Makefile
index 894f3ac1ce..7a738aaed5 100644
--- a/tests/periph_rtt_min/Makefile
+++ b/tests/periph_rtt_min/Makefile
@@ -11,15 +11,10 @@ RIOT_TERMINAL ?= socat
 include $(RIOTBASE)/Makefile.include
 
 # use highest possible RTT_FREQUENCY for boards that allow it
-ifneq (,$(filter stm32 nrf5%,$(CPU)))
+ifneq (,$(filter stm32 nrf5% sam% kinetis efm32 fe310,$(CPU)))
   RTT_FREQUENCY ?= RTT_MAX_FREQUENCY
   CFLAGS += -DRTT_FREQUENCY=$(RTT_FREQUENCY)
 endif
 
-# kinetis rtt runs at 1Hz, reduce samples to speed up the test
-ifneq (,$(filter kinetis,$(CPU)))
-  SAMPLES ?= 64
-else
-  SAMPLES ?= 1024
-endif
+SAMPLES ?= 1024
 CFLAGS += -DSAMPLES=$(SAMPLES)