diff --git a/src/libCom/osi/os/vxWorks/osdThread.c b/src/libCom/osi/os/vxWorks/osdThread.c
index b3d54c118..b3f2009c5 100644
--- a/src/libCom/osi/os/vxWorks/osdThread.c
+++ b/src/libCom/osi/os/vxWorks/osdThread.c
@@ -51,16 +51,28 @@ static SEM_ID threadOnceMutex = 0;
 /* osi =  199 - vx */
 
 static unsigned int getOsiPriorityValue(int ossPriority)
-{
-    return(199-ossPriority);
+{   
+    if ( ossPriority < 100 ) {
+        return threadPriorityMax;
+    }
+    else if ( ossPriority > 199 ) {
+        return threadPriorityMin;
+    }
+    else {
+        return ( 199u - (unsigned int) ossPriority );
+    }
 }
 
 static int getOssPriorityValue(unsigned int osiPriority)
 {
-    return(199 - osiPriority);
+    if ( osiPriority > 99 ) {
+        return 100;
+    }
+    else {
+        return ( 199 - (signed int) osiPriority );
+    }
 }
 
-
 unsigned int threadGetStackSize (threadStackSizeClass stackSizeClass) 
 {