diff --git a/boards/common/slwstk6000b/include/periph_conf.h b/boards/common/slwstk6000b/include/periph_conf.h
index 628d19778e..79ab2c8ee7 100644
--- a/boards/common/slwstk6000b/include/periph_conf.h
+++ b/boards/common/slwstk6000b/include/periph_conf.h
@@ -148,7 +148,7 @@ static const timer_conf_t timer_config[] = {
             .cmu = cmuClock_TIMER1
         },
         .irq = TIMER1_IRQn,
-        .channel_numof = 4
+        .channel_numof = 3
     },
     {
         .prescaler = {
diff --git a/boards/ikea-tradfri/include/periph_conf.h b/boards/ikea-tradfri/include/periph_conf.h
index 16941596d0..4363398704 100644
--- a/boards/ikea-tradfri/include/periph_conf.h
+++ b/boards/ikea-tradfri/include/periph_conf.h
@@ -125,7 +125,7 @@ static const timer_conf_t timer_config[] = {
             .cmu = cmuClock_TIMER1
         },
         .irq = TIMER1_IRQn,
-        .channel_numof = 4
+        .channel_numof = 3
     },
     {
         .prescaler = {
diff --git a/boards/slstk3401a/include/periph_conf.h b/boards/slstk3401a/include/periph_conf.h
index d2e061c230..cb3753937e 100644
--- a/boards/slstk3401a/include/periph_conf.h
+++ b/boards/slstk3401a/include/periph_conf.h
@@ -155,7 +155,7 @@ static const timer_conf_t timer_config[] = {
             .cmu = cmuClock_TIMER1
         },
         .irq = TIMER1_IRQn,
-        .channel_numof = 4
+        .channel_numof = 3
     },
     {
         .prescaler = {
diff --git a/boards/slstk3402a/include/periph_conf.h b/boards/slstk3402a/include/periph_conf.h
index dde763fc4a..4db7ef2723 100644
--- a/boards/slstk3402a/include/periph_conf.h
+++ b/boards/slstk3402a/include/periph_conf.h
@@ -146,7 +146,7 @@ static const timer_conf_t timer_config[] = {
             .cmu = cmuClock_WTIMER1
         },
         .irq = WTIMER1_IRQn,
-        .channel_numof = 4
+        .channel_numof = 3
     },
     {
         .prescaler = {
@@ -158,7 +158,7 @@ static const timer_conf_t timer_config[] = {
             .cmu = cmuClock_TIMER1
         },
         .irq = TIMER1_IRQn,
-        .channel_numof = 4
+        .channel_numof = 3
     },
     {
         .prescaler = {
diff --git a/boards/sltb001a/include/periph_conf.h b/boards/sltb001a/include/periph_conf.h
index e6de0d5690..f1438857de 100644
--- a/boards/sltb001a/include/periph_conf.h
+++ b/boards/sltb001a/include/periph_conf.h
@@ -155,7 +155,7 @@ static const timer_conf_t timer_config[] = {
             .cmu = cmuClock_TIMER1
         },
         .irq = TIMER1_IRQn,
-        .channel_numof = 4
+        .channel_numof = 3
     },
     {
         .prescaler = {