Make the compiler work-around more specific
diff --git a/library/bignum.c b/library/bignum.c
index d9a22c1..6d49caa 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1233,13 +1233,16 @@
         else
         {
             /*
-             * The version of Clang shipped by Apple with Mavericks can't
-             * handle 128-bit division properly. Disable 128-bits division
-             * for Clang on Apple for now, while waiting for more input on the
-             * exact version(s) affected and their identification macros.
+             * The version of Clang shipped by Apple with Mavericks around
+             * 2014-03 can't handle 128-bit division properly. Disable
+             * 128-bits division for this version. Let's be optimistic and
+             * assume it'll be fixed in the next minor version (next
+             * patchlevel is probably a bit too optimistic).
              */
-#if defined(POLARSSL_HAVE_UDBL) && \
-    ! ( defined(__x86_64__) && defined(__clang__) && defined(__APPLE__) )
+#if defined(POLARSSL_HAVE_UDBL) &&                          \
+    ! ( defined(__x86_64__) && defined(__APPLE__) &&        \
+        defined(__clang_major__) && __clang_major__ == 5 && \
+        defined(__clang_minor__) && __clang_minor__ == 0 )
             t_udbl r;
 
             r  = (t_udbl) X.p[i] << biL;