diff --git a/cpu/cc2538/Makefile b/cpu/cc2538/Makefile
index 5d00c79fadf5cdacf510d69d901f9bc3f92743b4..069fc4e400d4e2d342c1ce1ae30f0bb95da282c4 100644
--- a/cpu/cc2538/Makefile
+++ b/cpu/cc2538/Makefile
@@ -6,7 +6,7 @@ DIRS = periph $(RIOTCPU)/cortexm_common
 
 # cc2538_rf radio driver
 ifneq (,$(filter cc2538_rf,$(USEMODULE)))
-    DIRS += radio
+  DIRS += radio
 endif
 
 # (file triggers compiler bug. see #5775)
diff --git a/cpu/native/Makefile b/cpu/native/Makefile
index 9495a44a83b380a1e3071db939513880ecafb677..55c4961b4eda3c688a67bf104ee912352a8110c8 100644
--- a/cpu/native/Makefile
+++ b/cpu/native/Makefile
@@ -4,14 +4,14 @@ DIRS += periph
 DIRS += vfs
 
 ifneq (,$(filter netdev_tap,$(USEMODULE)))
-	DIRS += netdev_tap
+  DIRS += netdev_tap
 endif
 ifneq (,$(filter mtd_native,$(USEMODULE)))
-	DIRS += mtd
+  DIRS += mtd
 endif
 
 ifneq (,$(filter can_linux,$(USEMODULE)))
-        DIRS += can
+  DIRS += can
 endif
 
 include $(RIOTBASE)/Makefile.base
diff --git a/cpu/nrf5x_common/Makefile b/cpu/nrf5x_common/Makefile
index 6f68314295e5878c3ba69ea07a036e73bee9c8f4..ef599b387d5510d053d265cd2ddfea8ed0686619 100644
--- a/cpu/nrf5x_common/Makefile
+++ b/cpu/nrf5x_common/Makefile
@@ -3,7 +3,7 @@ DIRS = periph
 
 # build one of the radio drivers, if enabled
 ifneq (,$(filter nrfmin,$(USEMODULE)))
-    DIRS += radio/nrfmin
+  DIRS += radio/nrfmin
 endif
 
 include $(RIOTBASE)/Makefile.base
diff --git a/pkg/spiffs/Makefile.include b/pkg/spiffs/Makefile.include
index 975c3ddc2f9b0bf9abe097d69231d38ae8a7fc64..d25a221f4ec3f83915be64b6e26e5a1f48a083a0 100644
--- a/pkg/spiffs/Makefile.include
+++ b/pkg/spiffs/Makefile.include
@@ -2,5 +2,5 @@ INCLUDES += -I$(RIOTPKG)/spiffs/include
 INCLUDES += -I$(PKGDIRBASE)/spiffs/riotbuild/
 
 ifneq (,$(filter spiffs_fs,$(USEMODULE)))
-    DIRS += $(RIOTBASE)/pkg/spiffs/fs
+  DIRS += $(RIOTBASE)/pkg/spiffs/fs
 endif
diff --git a/sys/Makefile b/sys/Makefile
index 741f1d373040044367333b7c3dcdae82aa4f2cef..38a50741b75b1cecd3f37bdce629e36fac64df01 100644
--- a/sys/Makefile
+++ b/sys/Makefile
@@ -1,125 +1,125 @@
 ifneq (,$(filter csma_sender,$(USEMODULE)))
-    DIRS += net/link_layer/csma_sender
+  DIRS += net/link_layer/csma_sender
 endif
 ifneq (,$(filter posix_semaphore,$(USEMODULE)))
-    DIRS += posix/semaphore
+  DIRS += posix/semaphore
 endif
 ifneq (,$(filter posix_sockets,$(USEMODULE)))
-    DIRS += posix/sockets
+  DIRS += posix/sockets
 endif
 ifneq (,$(filter pthread,$(USEMODULE)))
-    DIRS += posix/pthread
+  DIRS += posix/pthread
 endif
 ifneq (,$(filter shell_commands,$(USEMODULE)))
-    DIRS += shell/commands
+  DIRS += shell/commands
 endif
 ifneq (,$(filter net_help,$(USEMODULE)))
-    DIRS += net/crosslayer/net_help
+  DIRS += net/crosslayer/net_help
 endif
 ifneq (,$(filter routing,$(USEMODULE)))
-    DIRS += net/routing
+  DIRS += net/routing
 endif
 ifneq (,$(filter oneway_malloc,$(USEMODULE)))
-    DIRS += oneway-malloc
+  DIRS += oneway-malloc
 endif
 ifneq (,$(filter ieee802154,$(USEMODULE)))
-    DIRS += net/link_layer/ieee802154
+  DIRS += net/link_layer/ieee802154
 endif
 ifneq (,$(filter netdev_test,$(USEMODULE)))
-    DIRS += net/netdev_test
+  DIRS += net/netdev_test
 endif
 ifneq (,$(filter icmpv6,$(USEMODULE)))
-    DIRS += net/network_layer/icmpv6
+  DIRS += net/network_layer/icmpv6
 endif
 ifneq (,$(filter ipv4_addr,$(USEMODULE)))
-    DIRS += net/network_layer/ipv4/addr
+  DIRS += net/network_layer/ipv4/addr
 endif
 ifneq (,$(filter ipv6_addr,$(USEMODULE)))
-    DIRS += net/network_layer/ipv6/addr
+  DIRS += net/network_layer/ipv6/addr
 endif
 ifneq (,$(filter ipv6_ext_rh,$(USEMODULE)))
-    DIRS += net/network_layer/ipv6/ext/rh
+  DIRS += net/network_layer/ipv6/ext/rh
 endif
 ifneq (,$(filter ipv6_ext,$(USEMODULE)))
-    DIRS += net/network_layer/ipv6/ext
+  DIRS += net/network_layer/ipv6/ext
 endif
 ifneq (,$(filter ipv6_hdr,$(USEMODULE)))
-    DIRS += net/network_layer/ipv6/hdr
+  DIRS += net/network_layer/ipv6/hdr
 endif
 ifneq (,$(filter gnrc gnrc_%,$(USEMODULE)))
-    DIRS += net/gnrc
+  DIRS += net/gnrc
 endif
 ifneq (,$(filter inet_csum,$(USEMODULE)))
-    DIRS += net/crosslayer/inet_csum
+  DIRS += net/crosslayer/inet_csum
 endif
 ifneq (,$(filter cipher_modes,$(USEMODULE)))
-    DIRS += crypto/modes
+  DIRS += crypto/modes
 endif
 ifneq (,$(filter nhdp,$(USEMODULE)))
-    DIRS += net/routing/nhdp
+  DIRS += net/routing/nhdp
 endif
 ifneq (,$(filter gnrc_netdev,$(USEMODULE)))
-    DIRS += net/gnrc/link_layer/netdev
+  DIRS += net/gnrc/link_layer/netdev
 endif
 ifneq (,$(filter fib,$(USEMODULE)))
-    DIRS += net/network_layer/fib
+  DIRS += net/network_layer/fib
 endif
 ifneq (,$(filter sixlowpan,$(USEMODULE)))
-    DIRS += net/network_layer/sixlowpan
+  DIRS += net/network_layer/sixlowpan
 endif
 ifneq (,$(filter log_%,$(USEMODULE)))
-    DIRS += log
+  DIRS += log
 endif
 ifneq (,$(filter xtimer,$(USEMODULE)))
-    DIRS += xtimer
+  DIRS += xtimer
 endif
 ifneq (,$(filter cpp11-compat,$(USEMODULE)))
-    DIRS += cpp11-compat
+  DIRS += cpp11-compat
 endif
 ifneq (,$(filter udp,$(USEMODULE)))
-    DIRS += net/transport_layer/udp
+  DIRS += net/transport_layer/udp
 endif
 ifneq (,$(filter tcp,$(USEMODULE)))
-    DIRS += net/transport_layer/tcp
+  DIRS += net/transport_layer/tcp
 endif
 ifneq (,$(filter hamming256,$(USEMODULE)))
-    DIRS += ecc/hamming256
+  DIRS += ecc/hamming256
 endif
 ifneq (,$(filter uhcpc,$(USEMODULE)))
-    DIRS += net/application_layer/uhcp
+  DIRS += net/application_layer/uhcp
 endif
 ifneq (,$(filter gnrc_uhcpc,$(USEMODULE)))
-    DIRS += net/gnrc/application_layer/uhcpc
+  DIRS += net/gnrc/application_layer/uhcpc
 endif
 ifneq (,$(filter sntp,$(USEMODULE)))
-    DIRS += net/application_layer/sntp
+  DIRS += net/application_layer/sntp
 endif
 ifneq (,$(filter netopt,$(USEMODULE)))
-    DIRS += net/crosslayer/netopt
+  DIRS += net/crosslayer/netopt
 endif
 ifneq (,$(filter sema,$(USEMODULE)))
-    DIRS += sema
+  DIRS += sema
 endif
 ifneq (,$(filter gcoap,$(USEMODULE)))
-    DIRS += net/application_layer/gcoap
+  DIRS += net/application_layer/gcoap
 endif
 ifneq (,$(filter emcute,$(USEMODULE)))
-    DIRS += net/application_layer/emcute
+  DIRS += net/application_layer/emcute
 endif
 ifneq (,$(filter sock_util,$(USEMODULE)))
-    DIRS += net/sock
+  DIRS += net/sock
 endif
 ifneq (,$(filter sock_dns,$(USEMODULE)))
-    DIRS += net/application_layer/dns
+  DIRS += net/application_layer/dns
 endif
 ifneq (,$(filter constfs,$(USEMODULE)))
-    DIRS += fs/constfs
+  DIRS += fs/constfs
 endif
 ifneq (,$(filter devfs,$(USEMODULE)))
-    DIRS += fs/devfs
+  DIRS += fs/devfs
 endif
 ifneq (,$(filter l2filter,$(USEMODULE)))
-    DIRS += net/link_layer/l2filter
+  DIRS += net/link_layer/l2filter
 endif
 
 DIRS += $(dir $(wildcard $(addsuffix /Makefile, ${USEMODULE})))
diff --git a/sys/auto_init/Makefile b/sys/auto_init/Makefile
index 699b4ab2223f8127ee7439a857e9289c39d2c3ed..1c2c0816d40fbc539760206fb585ffbce6a4f040 100644
--- a/sys/auto_init/Makefile
+++ b/sys/auto_init/Makefile
@@ -1,17 +1,17 @@
 ifneq (,$(filter auto_init_gnrc_netif,$(USEMODULE)))
-DIRS += netif
+  DIRS += netif
 endif
 
 ifneq (,$(filter auto_init_saul,$(USEMODULE)))
-DIRS += saul
+  DIRS += saul
 endif
 
 ifneq (,$(filter auto_init_storage,$(USEMODULE)))
-DIRS += storage
+  DIRS += storage
 endif
 
 ifneq (,$(filter auto_init_can,$(USEMODULE)))
-DIRS += can
+  DIRS += can
 endif
 
 include $(RIOTBASE)/Makefile.base
diff --git a/sys/can/Makefile b/sys/can/Makefile
index f6f3dc0f410ac41a42f85e898f4542154dae34fa..ea01f90d5335ebb0b70d081f6037eb6e8cb24ab9 100644
--- a/sys/can/Makefile
+++ b/sys/can/Makefile
@@ -1,10 +1,10 @@
 
 ifneq (,$(filter can_isotp,$(USEMODULE)))
-    DIRS += isotp
+  DIRS += isotp
 endif
 
 ifneq (,$(filter conn_can,$(USEMODULE)))
-    DIRS += conn
+  DIRS += conn
 endif
 
 include $(RIOTBASE)/Makefile.base
diff --git a/sys/net/gnrc/Makefile b/sys/net/gnrc/Makefile
index 7b9670b4fe6a8a27181a80636a01817114208a64..777878da6dc6b54d7d503f41e13c5c6506bb0a1e 100644
--- a/sys/net/gnrc/Makefile
+++ b/sys/net/gnrc/Makefile
@@ -1,137 +1,137 @@
 ifneq (,$(filter gnrc_icmpv6,$(USEMODULE)))
-    DIRS += network_layer/icmpv6
+  DIRS += network_layer/icmpv6
 endif
 ifneq (,$(filter gnrc_icmpv6_echo,$(USEMODULE)))
-    DIRS += network_layer/icmpv6/echo
+  DIRS += network_layer/icmpv6/echo
 endif
 ifneq (,$(filter gnrc_icmpv6_error,$(USEMODULE)))
-    DIRS += network_layer/icmpv6/error
+  DIRS += network_layer/icmpv6/error
 endif
 ifneq (,$(filter gnrc_ipv6,$(USEMODULE)))
-    DIRS += network_layer/ipv6
+  DIRS += network_layer/ipv6
 endif
 ifneq (,$(filter gnrc_ipv6_ext,$(USEMODULE)))
-    DIRS += network_layer/ipv6/ext
+  DIRS += network_layer/ipv6/ext
 endif
 ifneq (,$(filter gnrc_ipv6_hdr,$(USEMODULE)))
-    DIRS += network_layer/ipv6/hdr
+  DIRS += network_layer/ipv6/hdr
 endif
 ifneq (,$(filter gnrc_ipv6_nc,$(USEMODULE)))
-    DIRS += network_layer/ipv6/nc
+  DIRS += network_layer/ipv6/nc
 endif
 ifneq (,$(filter gnrc_ipv6_netif,$(USEMODULE)))
-    DIRS += network_layer/ipv6/netif
+  DIRS += network_layer/ipv6/netif
 endif
 ifneq (,$(filter gnrc_ipv6_nib,$(USEMODULE)))
-    DIRS += network_layer/ipv6/nib
+  DIRS += network_layer/ipv6/nib
 endif
 ifneq (,$(filter gnrc_ipv6_whitelist,$(USEMODULE)))
-    DIRS += network_layer/ipv6/whitelist
+  DIRS += network_layer/ipv6/whitelist
 endif
 ifneq (,$(filter gnrc_ipv6_blacklist,$(USEMODULE)))
-    DIRS += network_layer/ipv6/blacklist
+  DIRS += network_layer/ipv6/blacklist
 endif
 ifneq (,$(filter gnrc_ndp,$(USEMODULE)))
-    DIRS += network_layer/ndp
+  DIRS += network_layer/ndp
 endif
 ifneq (,$(filter gnrc_ndp_internal,$(USEMODULE)))
-    DIRS += network_layer/ndp/internal
+  DIRS += network_layer/ndp/internal
 endif
 ifneq (,$(filter gnrc_ndp_host,$(USEMODULE)))
-    DIRS += network_layer/ndp/host
+  DIRS += network_layer/ndp/host
 endif
 ifneq (,$(filter gnrc_ndp_node,$(USEMODULE)))
-    DIRS += network_layer/ndp/node
+  DIRS += network_layer/ndp/node
 endif
 ifneq (,$(filter gnrc_ndp_router,$(USEMODULE)))
-    DIRS += network_layer/ndp/router
+  DIRS += network_layer/ndp/router
 endif
 ifneq (,$(filter gnrc_netapi,$(USEMODULE)))
-    DIRS += netapi
+  DIRS += netapi
 endif
 ifneq (,$(filter gnrc_netif,$(USEMODULE)))
-    DIRS += netif
+  DIRS += netif
 endif
 ifneq (,$(filter gnrc_netif_hdr,$(USEMODULE)))
-    DIRS += netif/hdr
+  DIRS += netif/hdr
 endif
 ifneq (,$(filter gnrc_netreg,$(USEMODULE)))
-    DIRS += netreg
+  DIRS += netreg
 endif
 ifneq (,$(filter gnrc_nettest,$(USEMODULE)))
-    DIRS += nettest
+  DIRS += nettest
 endif
 ifneq (,$(filter gnrc_mac,$(USEMODULE)))
-    DIRS += link_layer/gnrc_mac
+  DIRS += link_layer/gnrc_mac
 endif
 ifneq (,$(filter gnrc_pkt,$(USEMODULE)))
-    DIRS += pkt
+  DIRS += pkt
 endif
 ifneq (,$(filter gnrc_lwmac,$(USEMODULE)))
-    DIRS += link_layer/lwmac
+  DIRS += link_layer/lwmac
 endif
 ifneq (,$(filter gnrc_pktbuf_static,$(USEMODULE)))
-    DIRS += pktbuf_static
+  DIRS += pktbuf_static
 endif
 ifneq (,$(filter gnrc_pktbuf,$(USEMODULE)))
-    DIRS += pktbuf
+  DIRS += pktbuf
 endif
 ifneq (,$(filter gnrc_priority_pktqueue,$(USEMODULE)))
-    DIRS += priority_pktqueue
+  DIRS += priority_pktqueue
 endif
 ifneq (,$(filter gnrc_pktdump,$(USEMODULE)))
-    DIRS += pktdump
+  DIRS += pktdump
 endif
 ifneq (,$(filter gnrc_rpl,$(USEMODULE)))
-    DIRS += routing/rpl
+  DIRS += routing/rpl
 endif
 ifneq (,$(filter gnrc_rpl_srh,$(USEMODULE)))
-    DIRS += routing/rpl/srh
+  DIRS += routing/rpl/srh
 endif
 ifneq (,$(filter gnrc_rpl_p2p,$(USEMODULE)))
-    DIRS += routing/rpl/p2p
+  DIRS += routing/rpl/p2p
 endif
 ifneq (,$(filter gnrc_sixlowpan,$(USEMODULE)))
-    DIRS += network_layer/sixlowpan
+  DIRS += network_layer/sixlowpan
 endif
 ifneq (,$(filter gnrc_sixlowpan_ctx,$(USEMODULE)))
-    DIRS += network_layer/sixlowpan/ctx
+  DIRS += network_layer/sixlowpan/ctx
 endif
 ifneq (,$(filter gnrc_sixlowpan_frag,$(USEMODULE)))
-    DIRS += network_layer/sixlowpan/frag
+  DIRS += network_layer/sixlowpan/frag
 endif
 ifneq (,$(filter gnrc_sixlowpan_iphc,$(USEMODULE)))
-    DIRS += network_layer/sixlowpan/iphc
+  DIRS += network_layer/sixlowpan/iphc
 endif
 ifneq (,$(filter gnrc_sixlowpan_nd,$(USEMODULE)))
-    DIRS += network_layer/sixlowpan/nd
+  DIRS += network_layer/sixlowpan/nd
 endif
 ifneq (,$(filter gnrc_sixlowpan_nd_router,$(USEMODULE)))
-    DIRS += network_layer/sixlowpan/nd/router
+  DIRS += network_layer/sixlowpan/nd/router
 endif
 ifneq (,$(filter gnrc_sixlowpan_netif,$(USEMODULE)))
-    DIRS += network_layer/sixlowpan/netif
+  DIRS += network_layer/sixlowpan/netif
 endif
 ifneq (,$(filter gnrc_slip,$(USEMODULE)))
-    DIRS += link_layer/slip
+  DIRS += link_layer/slip
 endif
 ifneq (,$(filter gnrc_sock,$(USEMODULE)))
-    DIRS += sock
+  DIRS += sock
 endif
 ifneq (,$(filter gnrc_sock_ip,$(USEMODULE)))
-    DIRS += sock/ip
+  DIRS += sock/ip
 endif
 ifneq (,$(filter gnrc_sock_udp,$(USEMODULE)))
-    DIRS += sock/udp
+  DIRS += sock/udp
 endif
 ifneq (,$(filter gnrc_udp,$(USEMODULE)))
-    DIRS += transport_layer/udp
+  DIRS += transport_layer/udp
 endif
 ifneq (,$(filter gnrc_tcp,$(USEMODULE)))
-    DIRS += transport_layer/tcp
+  DIRS += transport_layer/tcp
 endif
 ifneq (,$(filter gnrc_tftp,$(USEMODULE)))
-    DIRS += application_layer/tftp
+  DIRS += application_layer/tftp
 endif
 
 include $(RIOTBASE)/Makefile.base
diff --git a/sys/random/Makefile b/sys/random/Makefile
index 17568988a9b3899ae5c35d35c115c20238cfd754..372beceac515d95746396f34e8deb2306d97f80f 100644
--- a/sys/random/Makefile
+++ b/sys/random/Makefile
@@ -2,7 +2,7 @@ BASE_MODULE := prng
 SUBMODULES := 1
 
 ifneq (,$(filter prng_tinymt32,$(USEMODULE)))
-    DIRS += tinymt32
+  DIRS += tinymt32
 endif
 
 include $(RIOTBASE)/Makefile.base