diff --git a/repos/base/mk/generic.mk b/repos/base/mk/generic.mk
index 60655e8c90..a67c445396 100644
--- a/repos/base/mk/generic.mk
+++ b/repos/base/mk/generic.mk
@@ -77,7 +77,7 @@ endif
 CUSTOM_ADA_MAKE    ?= $(GNATMAKE)
 CUSTOM_ADA_FLAGS   ?= -q -c --GCC=$(CC) --RTS=$(ADA_RTS)
 CUSTOM_ADA_OPT     ?= -cargs $(CC_ADA_OPT)
-CUSTOM_ADA_INCLUDE ?= $(INCLUDES)
+CUSTOM_ADA_INCLUDE ?= -I- $(INCLUDES)
 
 %.o: %.adb
 	$(MSG_COMP)$@