diff --git a/Makefile b/Makefile
index fc9d89498b..fd4421eeb8 100644
--- a/Makefile
+++ b/Makefile
@@ -146,6 +146,9 @@ all::
 # algorithm. This is slower, but may detect attempted collision attacks.
 # Takes priority over other *_SHA1 knobs.
 #
+# Define OPENSSL_SHA1 environment variable when running make to link
+# with the SHA1 routine from openssl library.
+#
 # Define SHA1_MAX_BLOCK_SIZE to limit the amount of data that will be hashed
 # in one call to the platform's SHA1_Update(). e.g. APPLE_COMMON_CRYPTO
 # wants 'SHA1_MAX_BLOCK_SIZE=1024L*1024L*1024L' defined.
@@ -1390,10 +1393,9 @@ ifdef APPLE_COMMON_CRYPTO
 	SHA1_MAX_BLOCK_SIZE = 1024L*1024L*1024L
 endif
 
-ifdef DC_SHA1
-	LIB_OBJS += sha1dc/sha1.o
-	LIB_OBJS += sha1dc/ubc_check.o
-	BASIC_CFLAGS += -DSHA1_DC
+ifdef OPENSSL_SHA1
+	EXTLIBS += $(LIB_4_CRYPTO)
+	BASIC_CFLAGS += -DSHA1_OPENSSL
 else
 ifdef BLK_SHA1
 	LIB_OBJS += block-sha1/sha1.o
@@ -1407,8 +1409,10 @@ ifdef APPLE_COMMON_CRYPTO
 	COMPAT_CFLAGS += -DCOMMON_DIGEST_FOR_OPENSSL
 	BASIC_CFLAGS += -DSHA1_APPLE
 else
-	EXTLIBS += $(LIB_4_CRYPTO)
-	BASIC_CFLAGS += -DSHA1_OPENSSL
+	DC_SHA1 := YesPlease
+	LIB_OBJS += sha1dc/sha1.o
+	LIB_OBJS += sha1dc/ubc_check.o
+	BASIC_CFLAGS += -DSHA1_DC
 endif
 endif
 endif