diff --git a/Makefile b/Makefile
index 6baad1669e..8d33936a12 100644
--- a/Makefile
+++ b/Makefile
@@ -989,6 +989,10 @@ EXTLIBS =
 
 GIT_USER_AGENT = git/$(GIT_VERSION)
 
+ifeq ($(wildcard sha1collisiondetection/lib/sha1.h),sha1collisiondetection/lib/sha1.h)
+DC_SHA1_SUBMODULE = auto
+endif
+
 include config.mak.uname
 -include config.mak.autogen
 -include config.mak