diff --git a/src/sha1.cpp b/src/sha1.cpp
index 8930673..8cc4df7 100644
--- a/src/sha1.cpp
+++ b/src/sha1.cpp
@@ -27,9 +27,9 @@
 
 /* this is only to get definitions for memcpy(), ntohl() and htonl() */
 //#include "../git-compat-util.h"
+extern "C" {
 #include <string.h>
 #include "sha1.h"
-
 #ifndef WIN32
 #include <arpa/inet.h>
 #else
@@ -326,3 +326,4 @@ void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx)
     for (i = 0; i < 5; i++)
         put_be32(hashout + i*4, ctx->H[i]);
 }
+}
diff --git a/src/sha1.h b/src/sha1.h
index 7448b70..ae6148c 100644
--- a/src/sha1.h
+++ b/src/sha1.h
@@ -25,17 +25,21 @@
  * none of the original Mozilla code remains.
  */
 
-typedef struct {
-    unsigned long long size;
-    unsigned int H[5];
-    unsigned int W[16];
-} blk_SHA_CTX;
+extern "C" {
 
-void blk_SHA1_Init(blk_SHA_CTX *ctx);
-void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, unsigned long len);
-void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);
+    typedef struct {
+        unsigned long long size;
+        unsigned int H[5];
+        unsigned int W[16];
+    } blk_SHA_CTX;
+
+    void blk_SHA1_Init(blk_SHA_CTX *ctx);
+    void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, unsigned long len);
+    void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);
 
 #define git_SHA_CTX	blk_SHA_CTX
 #define git_SHA1_Init	blk_SHA1_Init
 #define git_SHA1_Update	blk_SHA1_Update
 #define git_SHA1_Final	blk_SHA1_Final
+
+}