diff --git a/src/pcas/build/Makefile b/src/pcas/build/Makefile
index 7da07236e..d45b9f469 100644
--- a/src/pcas/build/Makefile
+++ b/src/pcas/build/Makefile
@@ -81,10 +81,9 @@ USR_CXXFLAGS_RTEMS = -fno-strict-aliasing
 USR_CXXFLAGS_vxWorks = -fno-strict-aliasing
 
 # There is a bug in some vxWorks compilers that these work around:
-ifeq ($(VX_GNU_VERSION), 4.1.2)
-  casStreamOS_CXXFLAGS_vxWorks-ppc604_altivec = -O0
-  casStreamOS_CXXFLAGS_vxWorks-ppc604_long = -O0
-  casStreamOS_CXXFLAGS_vxWorks-ppc604 = -O0
+ifeq ($(VXWORKS_VERSION)$(filter -mcpu=604,$(ARCH_DEP_CFLAGS)), 6.6-mcpu=604)
+  casDGIntfOS_CXXFLAGS = -fno-inline
+  casStreamOS_CXXFLAGS = -fno-inline
 endif
 
 LIBRARY = cas