diff --git a/cpu/stm32/Makefile.features b/cpu/stm32/Makefile.features
index bccfeddd97..2362680238 100644
--- a/cpu/stm32/Makefile.features
+++ b/cpu/stm32/Makefile.features
@@ -18,7 +18,7 @@ ifneq (,$(filter $(CPU_FAM),l0 l1))
   FEATURES_PROVIDED += periph_eeprom
 endif
 
-ifeq (stm32f1,$(CPU_FAM))
+ifeq (f1,$(CPU_FAM))
   FEATURES_CONFLICT += periph_rtc:periph_rtt
   FEATURES_CONFLICT_MSG += "On the STM32F1, the RTC and RTT map to the same hardware peripheral."
 endif