diff --git a/cpu/cortexm_common/Makefile.include b/cpu/cortexm_common/Makefile.include
index 72dac672a8..eef3eb0092 100644
--- a/cpu/cortexm_common/Makefile.include
+++ b/cpu/cortexm_common/Makefile.include
@@ -70,8 +70,12 @@ else
 endif
 
 # Configure riotboot bootloader and slot lengths
-# 4KB are currently enough
-RIOTBOOT_LEN ?= 0x1000
+# 4KB are currently enough, set it to 16KB if USB-DFU is used
+ifneq (,$(filter usbus_dfu,$(USEMODULE)))
+  RIOTBOOT_LEN ?= 0x4000
+else
+  RIOTBOOT_LEN ?= 0x1000
+endif
 # Currently 2 slots are supported by default, equals in length
 NUM_SLOTS ?= 2
 # Take the whole flash minus RIOTBOOT_LEN and divide it by NUM_SLOTS