diff --git a/ChangeLog b/ChangeLog
index 3fe0600b2f2fb4f237c25da8c18023574ce91cb5..19fadaab7ca345d2a6f2350dd2f919de7f28b194 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+2015-08-25  Niels Möller  <nisse@lysator.liu.se>
+
+	* sha3.h (NETTLE_SHA3_FIPS202): New preprocessor constant.
+
 2015-08-24  Niels Möller  <nisse@lysator.liu.se>
 
 	* testsuite/sha3.awk: Document origin of test vectors.
diff --git a/sha3.h b/sha3.h
index 6435ad62dc4cb3846964d584e779f31af30e4784..0c655376492fc1fa1130833028316f034ae4fcde 100644
--- a/sha3.h
+++ b/sha3.h
@@ -40,6 +40,7 @@
 extern "C" {
 #endif
 
+/* Name mangling */
 #define sha3_permute nettle_sha3_permute
 #define _sha3_update _nettle_sha3_update
 #define _sha3_pad _nettle_sha3_pad
@@ -56,6 +57,9 @@ extern "C" {
 #define sha3_512_update nettle_sha3_512_update
 #define sha3_512_digest nettle_sha3_512_digest
 
+/* Indicates that SHA3 is the NIST FIPS 202 version. */
+#define NETTLE_SHA3_FIPS202 1
+
 /* The sha3 state is a 5x5 matrix of 64-bit words. In the notation of
    Keccak description, S[x,y] is element x + 5*y, so if x is
    interpreted as the row index and y the column index, it is stored