diff --git a/Makefile.dep b/Makefile.dep
index 584830b6f4..c8f975e40f 100644
--- a/Makefile.dep
+++ b/Makefile.dep
@@ -283,11 +283,11 @@ ifneq (,$(filter posix,$(USEMODULE)))
 endif
 
 ifneq (,$(filter posix_semaphore,$(USEMODULE)))
-  USEMODULE += sem
+  USEMODULE += sema
   USEMODULE += vtimer
 endif
 
-ifneq (,$(filter sem,$(USEMODULE)))
+ifneq (,$(filter sema,$(USEMODULE)))
   USEMODULE += vtimer
 endif
 
diff --git a/sys/Makefile b/sys/Makefile
index 8baba47737..226e3c02c6 100644
--- a/sys/Makefile
+++ b/sys/Makefile
@@ -71,8 +71,8 @@ endif
 ifneq (,$(filter netopt,$(USEMODULE)))
     DIRS += net/crosslayer/netopt
 endif
-ifneq (,$(filter sem,$(USEMODULE)))
-    DIRS += sem
+ifneq (,$(filter sema,$(USEMODULE)))
+    DIRS += sema
 endif
 
 DIRS += $(dir $(wildcard $(addsuffix /Makefile, ${USEMODULE})))
diff --git a/sys/include/sem.h b/sys/include/sema.h
similarity index 100%
rename from sys/include/sem.h
rename to sys/include/sema.h
diff --git a/sys/posix/include/semaphore.h b/sys/posix/include/semaphore.h
index cbf3fd64f9..1ffe83c1e4 100644
--- a/sys/posix/include/semaphore.h
+++ b/sys/posix/include/semaphore.h
@@ -26,7 +26,7 @@
 #include <errno.h>
 #include <time.h>
 
-#include "sem.h"
+#include "sema.h"
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/sys/posix/semaphore/posix_semaphore.c b/sys/posix/semaphore/posix_semaphore.c
index 4e8d67893c..1076aae08a 100644
--- a/sys/posix/semaphore/posix_semaphore.c
+++ b/sys/posix/semaphore/posix_semaphore.c
@@ -21,7 +21,7 @@
 
 #include "irq.h"
 #include "sched.h"
-#include "sem.h"
+#include "sema.h"
 #include "tcb.h"
 #include "timex.h"
 #include "thread.h"
diff --git a/sys/sem/Makefile b/sys/sema/Makefile
similarity index 100%
rename from sys/sem/Makefile
rename to sys/sema/Makefile
diff --git a/sys/sem/sem.c b/sys/sema/sema.c
similarity index 99%
rename from sys/sem/sem.c
rename to sys/sema/sema.c
index a4256069b7..0cc1cff90e 100644
--- a/sys/sem/sem.c
+++ b/sys/sema/sema.c
@@ -24,7 +24,7 @@
 #include "msg.h"
 #include "vtimer.h"
 
-#include "sem.h"
+#include "sema.h"
 
 #define ENABLE_DEBUG (0)
 #include "debug.h"