diff --git a/Makefile.pseudomodules b/Makefile.pseudomodules
index a91c8c63ea152548a62f519c4d9f1654ec1cab5a..2602805b4bea584f94b87fd866ee0ce91066d7df 100644
--- a/Makefile.pseudomodules
+++ b/Makefile.pseudomodules
@@ -3,9 +3,7 @@ PSEUDOMODULES += conn
 PSEUDOMODULES += conn_ip
 PSEUDOMODULES += conn_tcp
 PSEUDOMODULES += conn_udp
-PSEUDOMODULES += core_msg
-PSEUDOMODULES += core_mbox
-PSEUDOMODULES += core_thread_flags
+PSEUDOMODULES += core_%
 PSEUDOMODULES += emb6_router
 PSEUDOMODULES += gnrc_ipv6_default
 PSEUDOMODULES += gnrc_ipv6_router
diff --git a/core/Makefile b/core/Makefile
index 48422e909a47d7cd428d10fa73825060ccc8d8c2..4f12366947dd0fbb74c48a9b051b646c39f438ea 100644
--- a/core/Makefile
+++ b/core/Makefile
@@ -1 +1,7 @@
+# exclude submodule sources from *.c wildcard source selection
+SRC := $(filter-out mbox.c msg.c thread_flags.c,$(wildcard *.c))
+
+# enable submodules
+SUBMODULES := 1
+
 include $(RIOTBASE)/Makefile.base
diff --git a/core/mbox.c b/core/mbox.c
index 7c14f3514750e31004439a06ac5da7cceb65c95a..bd5e32415a7ff9ba18eba057cea35690256596c7 100644
--- a/core/mbox.c
+++ b/core/mbox.c
@@ -28,8 +28,6 @@
 #define ENABLE_DEBUG (0)
 #include "debug.h"
 
-#ifdef MODULE_CORE_MBOX
-
 static void _wake_waiter(thread_t *thread, unsigned irqstate)
 {
     sched_set_status(thread, STATUS_PENDING);
@@ -122,5 +120,3 @@ int _mbox_get(mbox_t *mbox, msg_t *msg, int blocking)
         return 0;
     }
 }
-
-#endif /* MODULE_CORE_MBOX */
diff --git a/core/msg.c b/core/msg.c
index 4ab2061411c56eb8b6741a6c1f6ca6b3d3fde4d1..190244cca8d9121181205a200fd8009e78ab996d 100644
--- a/core/msg.c
+++ b/core/msg.c
@@ -34,8 +34,6 @@
 #include "debug.h"
 #include "thread.h"
 
-#ifdef MODULE_CORE_MSG
-
 static int _msg_receive(msg_t *m, int block);
 static int _msg_send(msg_t *m, kernel_pid_t target_pid, bool block, unsigned state);
 
@@ -409,5 +407,3 @@ void msg_queue_print(void)
 
     irq_restore(state);
 }
-
-#endif /* MODULE_CORE_MSG */
diff --git a/core/thread_flags.c b/core/thread_flags.c
index 9396c31e30c555e2e7c08563bcd904fa219e06b9..281a592306ff3d1d3bff86d1d5c02e1064f8eea3 100644
--- a/core/thread_flags.c
+++ b/core/thread_flags.c
@@ -26,7 +26,6 @@
 #define ENABLE_DEBUG (0)
 #include "debug.h"
 
-#ifdef MODULE_CORE_THREAD_FLAGS
 static thread_flags_t _thread_flags_clear_atomic(thread_t *thread, thread_flags_t mask)
 {
     unsigned state = irq_disable();
@@ -133,4 +132,3 @@ void thread_flags_set(thread_t *thread, thread_flags_t mask)
         irq_restore(state);
     }
 }
-#endif /* MODULE_CORE_THREAD_FLAGS */