diff --git a/src/cas/build/singleThread/Makefile.Unix b/src/cas/build/singleThread/Makefile.Unix
index 0dc63a703..655960b70 100644
--- a/src/cas/build/singleThread/Makefile.Unix
+++ b/src/cas/build/singleThread/Makefile.Unix
@@ -11,7 +11,8 @@ include $(TOP)/config/CONFIG_BASE
 
 CXXCMPLR = STRICT
 
-USR_INCLUDES = -I$(SRC) -I$(OSSRC) -I$(IOSRC) -I$(CA)
+USR_INCLUDES = -I$(SRC) -I$(OSSRC) -I$(IOSRC) -I$(CA) \
+		-I$(TOP)/src/include/os/$(T_A)
 
 DEPLIBS_BASE = $(EPICS_BASE_LIB)