diff --git a/src/libCom/osi/epicsMutex.h b/src/libCom/osi/epicsMutex.h
index 606ce9fc7..731559c10 100644
--- a/src/libCom/osi/epicsMutex.h
+++ b/src/libCom/osi/epicsMutex.h
@@ -24,7 +24,7 @@ public:
     class invalidSemaphore {}; /* exception */
     class noMemory {}; /* exception */
 private:
-    mutable semMutexId id;
+    mutable epicsMutexId id;
 };
 #endif /*__cplusplus*/