diff --git a/src/libCom/osi/os/WIN32/osdThread.c b/src/libCom/osi/os/WIN32/osdThread.c
index 751557d7a..ebf612a19 100644
--- a/src/libCom/osi/os/WIN32/osdThread.c
+++ b/src/libCom/osi/os/WIN32/osdThread.c
@@ -433,7 +433,7 @@ epicsShareFunc epicsThreadBooleanStatus epicsShareAPI epicsThreadHighestPriority
 
     magnitude = osdPriorityMagFromPriorityOSI ( priority, stateCount );
 
-    if ( magnitude > 1u ) {
+    if ( magnitude > 0u ) {
         *pPriorityJustBelow = osiPriorityMagFromMagnitueOSD ( magnitude - 1u, stateCount );
         status = epicsThreadBooleanStatusSuccess;
     }