diff --git a/Makefile b/Makefile
index 527486f..e898975 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,5 @@
-
+# export the submodule flag so that crypto knows it's being built as a submodule
+export USE_CRYPTO_SUBMODULE=1
 DESTDIR=/usr/local
 PREFIX=mbedtls_