diff --git a/src/libCom/test/epicsTimerTest.cpp b/src/libCom/test/epicsTimerTest.cpp
index 3572cdd5d..12ebb5308 100644
--- a/src/libCom/test/epicsTimerTest.cpp
+++ b/src/libCom/test/epicsTimerTest.cpp
@@ -44,7 +44,7 @@ private:
     static epicsSingleton < tsFreeList < class delayVerify, 0x20 > > pFreeList;
 };
 
-static unsigned expireCount;
+static volatile unsigned expireCount;
 static epicsEvent expireEvent;
 
 delayVerify::delayVerify ( double expectedDelayIn, epicsTimerQueue &queueIn ) :