diff --git a/src/md5.c b/src/md5.c
index 01231b1..7f11da9 100644
--- a/src/md5.c
+++ b/src/md5.c
@@ -43,6 +43,9 @@
 	(cp)[3] = ((value) >> 24) & 0xFF; \
     } while(0)
 
+static void MD5Transform(uint32_t buf[4], const unsigned char inext[64],
+			 struct MD5Context *ctx);
+
 /*
  * Start MD5 accumulation.  Set bit count to 0 and buffer to mysterious
  * initialization constants.
@@ -179,8 +182,8 @@ void MD5Final(unsigned char digest[16], struct MD5Context *ctx)
  * reflect the addition of 16 longwords of new data.  MD5Update blocks
  * the data and converts bytes into longwords for this routine.
  */
-void MD5Transform(uint32_t buf[4], const unsigned char inext[64],
-	struct MD5Context *ctx)
+static void MD5Transform(uint32_t buf[4], const unsigned char inext[64],
+			 struct MD5Context *ctx)
 {
     register uint32_t a, b, c, d, i;
     uint32_t in[16];
diff --git a/src/md5.h b/src/md5.h
index 3095f95..1ce4cab 100644
--- a/src/md5.h
+++ b/src/md5.h
@@ -31,8 +31,6 @@ void MD5Init(struct MD5Context *context);
 void MD5Update(struct MD5Context *context, unsigned char const *buf,
 	       uint32_t len);
 void MD5Final(unsigned char digest[16], struct MD5Context *context);
-void MD5Transform(uint32_t buf[4], const unsigned char in[64],
-			struct MD5Context *ctx);
 
 #ifdef DEBUG_MD5
 void MD5DumpBytes(unsigned char *b, int len);