diff --git a/lib/md5.c b/lib/md5.c
index 1c201f321..d8344dbe4 100644
--- a/lib/md5.c
+++ b/lib/md5.c
@@ -96,13 +96,30 @@ static void MD5_Final(unsigned char digest[16], MD5_CTX * ctx)
               (__IPHONE_OS_VERSION_MAX_ALLOWED >= 20000))
 
 /* For Apple operating systems: CommonCrypto has the functions we need.
-   The library's headers are even backward-compatible with OpenSSL's
-   headers as long as we define COMMON_DIGEST_FOR_OPENSSL first.
-
    These functions are available on Tiger and later, as well as iOS 2.0
-   and later. If you're building for an older cat, well, sorry. */
-#  define COMMON_DIGEST_FOR_OPENSSL
+   and later. If you're building for an older cat, well, sorry.
+
+   Declaring the functions as static like this seems to be a bit more
+   reliable than defining COMMON_DIGEST_FOR_OPENSSL on older cats. */
 #  include <CommonCrypto/CommonDigest.h>
+#  define MD5_CTX CC_MD5_CTX
+
+static void MD5_Init(MD5_CTX *ctx)
+{
+  CC_MD5_Init(ctx);
+}
+
+static void MD5_Update(MD5_CTX *ctx,
+                       const unsigned char *input,
+                       unsigned int inputLen)
+{
+  CC_MD5_Update(ctx, input, inputLen);
+}
+
+static void MD5_Final(unsigned char digest[16], MD5_CTX *ctx)
+{
+  CC_MD5_Final(digest, ctx);
+}
 
 #elif defined(_WIN32)