diff --git a/cpu/kinetis/Makefile.dep b/cpu/kinetis/Makefile.dep
index 2728a327db..3a076de393 100644
--- a/cpu/kinetis/Makefile.dep
+++ b/cpu/kinetis/Makefile.dep
@@ -1,3 +1,8 @@
 ifneq (,$(filter periph_rtc,$(USEMODULE)))
   USEMODULE += periph_rtt
 endif
+ifneq (,$(filter periph_timer,$(USEMODULE)))
+  # RTT is used as the time base for the LPTMR driver.
+  # TODO: Remove when LPTMR is refactored.
+  FEATURES_OPTIONAL += periph_rtt
+endif