diff --git a/config/CONFIG_COMMON b/config/CONFIG_COMMON
index 9f0970a0a..a6baeaef1 100644
--- a/config/CONFIG_COMMON
+++ b/config/CONFIG_COMMON
@@ -178,7 +178,7 @@ EPICS_INCLUDES = -I$(INSTALL_INCLUDE)/os/$(OS_CLASS) -I$(INSTALL_INCLUDE)
 #       (convenience for extensions and applications)
 ifneq ($(EPICS_BASE),$(TOP))
 ifneq ($(EPICS_BASE),$(INSTALL_LOCATION))
-EPICS_INCLUDES += -I$(EPICS_BASE_INCLUDE)/os/$(OS_CLASS) += -I$(EPICS_BASE_INCLUDE)
+EPICS_INCLUDES += -I$(EPICS_BASE_INCLUDE)/os/$(OS_CLASS) -I$(EPICS_BASE_INCLUDE)
 endif
 endif