diff --git a/block-sha1/sha1.h b/block-sha1/sha1.h
index 9fb0441b98..47bb916636 100644
--- a/block-sha1/sha1.h
+++ b/block-sha1/sha1.h
@@ -16,7 +16,9 @@ void blk_SHA1_Init(blk_SHA_CTX *ctx);
 void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, size_t len);
 void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);
 
+#ifndef platform_SHA_CTX
 #define platform_SHA_CTX	blk_SHA_CTX
 #define platform_SHA1_Init	blk_SHA1_Init
 #define platform_SHA1_Update	blk_SHA1_Update
 #define platform_SHA1_Final	blk_SHA1_Final
+#endif
diff --git a/sha1/openssl.h b/sha1/openssl.h
index 006c1f4ba5..1038af47da 100644
--- a/sha1/openssl.h
+++ b/sha1/openssl.h
@@ -40,10 +40,12 @@ static inline void openssl_SHA1_Clone(struct openssl_SHA1_CTX *dst,
 	EVP_MD_CTX_copy_ex(dst->ectx, src->ectx);
 }
 
+#ifndef platform_SHA_CTX
 #define platform_SHA_CTX openssl_SHA1_CTX
 #define platform_SHA1_Init openssl_SHA1_Init
 #define platform_SHA1_Clone openssl_SHA1_Clone
 #define platform_SHA1_Update openssl_SHA1_Update
 #define platform_SHA1_Final openssl_SHA1_Final
+#endif
 
 #endif /* SHA1_OPENSSL_H */
diff --git a/sha1dc_git.h b/sha1dc_git.h
index 60e3ce8439..f6f880cabe 100644
--- a/sha1dc_git.h
+++ b/sha1dc_git.h
@@ -18,7 +18,10 @@ void git_SHA1DCFinal(unsigned char [20], SHA1_CTX *);
 void git_SHA1DCUpdate(SHA1_CTX *ctx, const void *data, unsigned long len);
 
 #define platform_SHA_IS_SHA1DC /* used by "test-tool sha1-is-sha1dc" */
+
+#ifndef platform_SHA_CTX
 #define platform_SHA_CTX SHA1_CTX
 #define platform_SHA1_Init git_SHA1DCInit
 #define platform_SHA1_Update git_SHA1DCUpdate
 #define platform_SHA1_Final git_SHA1DCFinal
+#endif