diff --git a/src/libCom/osi/os/posix/osdThread.c b/src/libCom/osi/os/posix/osdThread.c
index d9fc5bab8..3fa8e0ba9 100644
--- a/src/libCom/osi/os/posix/osdThread.c
+++ b/src/libCom/osi/os/posix/osdThread.c
@@ -184,8 +184,9 @@ void threadOnceOsd(threadOnceId *id, void (*func)(void *), void *arg)
 
     semMutexMustTake(onceMutex);
     if (*id == 0) {
-    	*id = 1;
+    	*id = -1;
     	func(arg);
+    	*id = 1;
     }
     semMutexGive(onceMutex);
 }
diff --git a/src/libCom/osi/osiThread.h b/src/libCom/osi/osiThread.h
index 200870c32..2cd7a5c37 100644
--- a/src/libCom/osi/osiThread.h
+++ b/src/libCom/osi/osiThread.h
@@ -44,7 +44,7 @@ epicsShareFunc void epicsShareAPI threadOnceOsd(
 #define threadOnce(id,func,arg) \
     do { \
 	threadOnceId *idCopy =(id); \
-	if(*idCopy == 0) \
+	if(*idCopy <= 0) \
 	    threadOnceOsd(idCopy,func,arg); \
     } while(0)