diff --git a/src/platforms/px4_posix.h b/src/platforms/px4_posix.h
index 3c138e5a70..9aa7c0e15a 100644
--- a/src/platforms/px4_posix.h
+++ b/src/platforms/px4_posix.h
@@ -64,7 +64,7 @@ typedef struct
 __EXPORT int		px4_sem_init(px4_sem_t *s, int pshared, unsigned value);
 __EXPORT int		px4_sem_wait(px4_sem_t *s);
 __EXPORT int		px4_sem_post(px4_sem_t *s);
-__EXPORT int		px4_sem_getvalue(px4_sem_t *s);
+__EXPORT int		px4_sem_getvalue(px4_sem_t *s, int *sval);
 __EXPORT int		px4_sem_destroy(px4_sem_t *s);
 
 __END_DECLS
@@ -75,8 +75,8 @@ typedef px4_sem_t		sem_t
 
 #define px4_sem_init		_GLOBAL sem_init
 #define px4_sem_wait		_GLOBAL sem_wait
-#define px4_sem_post		_GLOBAL px4_sem_post
-#define px4_sem_getvalue	_GLOBAL px4_sem_getvalue
+#define px4_sem_post		_GLOBAL sem_post
+#define px4_sem_getvalue	_GLOBAL sem_getvalue
 #define px4_sem_destroy		_GLOBAL sem_destroy
 
 
@@ -122,7 +122,7 @@ typedef struct {
   pollevent_t 	revents;  /* The output event flags */
 
   /* Required for PX4 compatability */
-  sem_t   *sem;  	/* Pointer to semaphore used to post output event */
+  px4_sem_t   *sem;  	/* Pointer to semaphore used to post output event */
   void   *priv;     	/* For use by drivers */
 } px4_pollfd_struct_t;