diff --git a/Makefile b/Makefile
index e53750ca01..aa680269e8 100644
--- a/Makefile
+++ b/Makefile
@@ -1497,7 +1497,9 @@ else
 	LIB_OBJS += sha1dc_git.o
 ifdef DC_SHA1_EXTERNAL
 	ifdef DC_SHA1_SUBMODULE
+		ifneq ($(DC_SHA1_SUBMODULE),auto)
 $(error Only set DC_SHA1_EXTERNAL or DC_SHA1_SUBMODULE, not both)
+		endif
 	endif
 	BASIC_CFLAGS += -DDC_SHA1_EXTERNAL
 	EXTLIBS += -lsha1detectcoll