diff --git a/src/libCom/Makefile b/src/libCom/Makefile
index 672b8c1db..3417d7b0f 100644
--- a/src/libCom/Makefile
+++ b/src/libCom/Makefile
@@ -57,8 +57,8 @@ INC += epicsSingleton.h
 INC += epicsGuard.h
 INC += epicsOnce.h
 SRCS += resourceLib.cpp
-SRCS += epicsSingletonBase.cpp
 SRCS += epicsOnce.cpp
+SRCS += epicsSingletonMutex.cpp
 
 SRC_DIRS += $(LIBCOM)/dbmf
 INC += dbmf.h