diff --git a/boards/same54-xpro/Makefile.include b/boards/same54-xpro/Makefile.include
index 9e5bbf58a1..f8f1b33e90 100644
--- a/boards/same54-xpro/Makefile.include
+++ b/boards/same54-xpro/Makefile.include
@@ -3,4 +3,11 @@
 # debugger.
 TTY_BOARD_FILTER := --model 'EDBG CMSIS-DAP'
 
+# Overwrite GCLK definitions, so that GCLK_IO[2..7] can be connected to GPIOs.
+# This way the frequency of signals, connected to these pins, can be measured
+# with the FREQM peripheral.
+CFLAGS += -DSAM0_GCLK_TIMER=8
+CFLAGS += -DSAM0_GCLK_PERIPH=9
+CFLAGS += -DSAM0_GCLK_100MHZ=10
+
 include $(RIOTMAKE)/boards/sam0.inc.mk