diff --git a/library/Makefile b/library/Makefile
index 430c598..f01b1a1 100644
--- a/library/Makefile
+++ b/library/Makefile
@@ -63,6 +63,13 @@
 endif
 endif
 
+
+ifdef USE_CRYPTO_SUBMODULE
+# Look in crypto for libmbedcrypto.
+LOCAL_LDFLAGS += -L../crypto/library
+LOCAL_CFLAGS += -I../crypto/include
+CRYPTO := ../crypto/library/
+else
 OBJS_CRYPTO=	aes.o		aesni.o		arc4.o		\
 		aria.o		asn1parse.o	asn1write.o	\
 		base64.o	bignum.o	blowfish.o	\
@@ -85,6 +92,8 @@
 		sha1.o		sha256.o	sha512.o	\
 		threading.o	timing.o	version.o	\
 		version_features.o		xtea.o
+CRYPTO :=
+endif
 
 OBJS_X509=	certs.o		pkcs11.o	x509.o		\
 		x509_create.o	x509_crl.o	x509_crt.o	\
@@ -148,7 +157,7 @@
 endif
 endif
 
-libmbedx509.$(SOEXT_X509): $(OBJS_X509) libmbedcrypto.so
+libmbedx509.$(SOEXT_X509): $(OBJS_X509) $(CRYPTO)libmbedcrypto.so
 	echo "  LD    $@"
 	$(CC) -shared -Wl,-soname,$@ -L. -lmbedcrypto $(LOCAL_LDFLAGS) $(LDFLAGS) -o $@ $(OBJS_X509)
 
@@ -165,6 +174,10 @@
 	$(CC) -shared -Wl,-soname,$@ -Wl,--out-implib,$@.a -o $@ $(OBJS_X509) -lws2_32 -lwinmm -lgdi32 -L. -lmbedcrypto -static-libgcc $(LOCAL_LDFLAGS) $(LDFLAGS)
 
 # crypto
+ifdef USE_CRYPTO_SUBMODULE
+libmbedcrypto.%:
+	$(MAKE) CRYPTO_INCLUDES:="-I../../include -I../include" -C ../crypto/library $@
+else
 libmbedcrypto.a: $(OBJS_CRYPTO)
 	echo "  AR    $@"
 	$(AR) $(ARFLAGS) $@ $(OBJS_CRYPTO)
@@ -190,6 +203,7 @@
 libmbedcrypto.dll: $(OBJS_CRYPTO)
 	echo "  LD    $@"
 	$(CC) -shared -Wl,-soname,$@ -Wl,--out-implib,$@.a -o $@ $(OBJS_CRYPTO) -lws2_32 -lwinmm -lgdi32 -static-libgcc $(LOCAL_LDFLAGS) $(LDFLAGS)
+endif
 
 .c.o:
 	echo "  CC    $<"