diff --git a/src/libCom/osi/os/RTEMS/osdThread.c b/src/libCom/osi/os/RTEMS/osdThread.c
index fb6f0052d..5959709df 100644
--- a/src/libCom/osi/os/RTEMS/osdThread.c
+++ b/src/libCom/osi/os/RTEMS/osdThread.c
@@ -361,25 +361,11 @@ void threadOnceOsd(threadOnceId *id, void(*func)(void *), void *arg)
 		rtems_task_mode(mode, RTEMS_PREEMPT_MASK, &mode);
 	}
 	semMutexMustTake(onceMutex);
-	switch (id->state) {
-	case 0:
-		id->state = -1;
-		id->sem = semMutexMustCreate();
-		semMutexMustTake(id->sem);
-		semMutexGive(onceMutex);
+	if (*id == 0) {
 		func(arg);
-		id->state = 1;
-		semBinaryGive(id->sem);
-		break;
-	case -1:
-		semMutexGive(onceMutex);
-		semBinaryMustTake(id->sem);
-		semBinaryGive(id->sem);
-		break;
-	default:
-		semMutexGive(onceMutex);
-		break;
+		*id = 1;
 	}
+	semMutexGive(onceMutex);
 }
 
 /*
diff --git a/src/libCom/osi/os/posix/osdThread.c b/src/libCom/osi/os/posix/osdThread.c
index 1d0e3baab..0231881bf 100644
--- a/src/libCom/osi/os/posix/osdThread.c
+++ b/src/libCom/osi/os/posix/osdThread.c
@@ -183,25 +183,11 @@ void threadOnceOsd(threadOnceId *id, void (*func)(void *), void *arg)
     checkStatusQuit(status,"pthread_once","threadOnce");
 
     semMutexMustTake(onceMutex);
-    switch (id->state) {
-    case 0:
-	id->state = -1;
-	id->mutex = semMutexMustCreate();
-	semMutexMustTake(id->mutex);
-	semMutexGive(onceMutex);
-	func(arg);
-	id->state = 1;
-	semMutexGive(id->mutex);
-	break;
-    case -1:
-	semMutexGive(onceMutex);
-	semMutexMustTake(id->mutex);
-	semMutexGive(id->mutex);
-	break;
-    default:
-	semMutexGive(onceMutex);
-	break;
+    if (*id == 0) {
+    	func(arg);
+    	*id = 1;
     }
+    semMutexGive(onceMutex);
 }
 
 static void * start_routine(void *arg)
diff --git a/src/libCom/osi/os/vxWorks/osdThread.c b/src/libCom/osi/os/vxWorks/osdThread.c
index e35fc7846..fb489de54 100644
--- a/src/libCom/osi/os/vxWorks/osdThread.c
+++ b/src/libCom/osi/os/vxWorks/osdThread.c
@@ -77,7 +77,7 @@ void threadOnceOsd(threadOnceId *id, void (*func)(void *), void *arg)
 {
     /* not a good implementation (no guarantee that func() has finished before
        the next task calls this routine); see the Posix implementation */
-    if(vxTas(&id->state))
+    if(vxTas(*id))
 	func(arg);
 }
 
diff --git a/src/libCom/osi/osiThread.h b/src/libCom/osi/osiThread.h
index 11875e121..200870c32 100644
--- a/src/libCom/osi/osiThread.h
+++ b/src/libCom/osi/osiThread.h
@@ -34,11 +34,9 @@ typedef enum {
 epicsShareFunc unsigned int epicsShareAPI threadGetStackSize(threadStackSizeClass size);
 
 /* threadOnce is a macro for efficiency (calls threadOnceOsd) */
-typedef struct {
-    int state; semMutexId mutex;
-} threadOnceId;
+typedef int threadOnceId;
 
-#define OSITHREAD_ONCE_INIT {0,0}
+#define OSITHREAD_ONCE_INIT 0
 
 epicsShareFunc void epicsShareAPI threadOnceOsd(
     threadOnceId *id, void (*func)(void *), void *arg);
@@ -46,7 +44,7 @@ epicsShareFunc void epicsShareAPI threadOnceOsd(
 #define threadOnce(id,func,arg) \
     do { \
 	threadOnceId *idCopy =(id); \
-	if((idCopy->state) <= 0) \
+	if(*idCopy == 0) \
 	    threadOnceOsd(idCopy,func,arg); \
     } while(0)