diff --git a/stratum/algos/zr5.c b/stratum/algos/zr5.c
index be196ba..ffb98e9 100644
--- a/stratum/algos/zr5.c
+++ b/stratum/algos/zr5.c
@@ -1,8 +1,7 @@
-#include "x15.h"
+#include <stdio.h>
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
-#include <stdio.h>
 
 #include "../sha3/sph_blake.h"
 #include "../sha3/sph_groestl.h"
@@ -10,6 +9,8 @@
 #include "../sha3/sph_keccak.h"
 #include "../sha3/sph_skein.h"
 
+//#define TEST_VERBOSELY
+
 #define ZR_BLAKE   0
 #define ZR_GROESTL 1
 #define ZR_JH      2
@@ -47,7 +48,7 @@ static const int permut[][4] = {
 	{3, 2, 1, 0}
 };
 
-void zr5_hash(const char* input, char* output, uint32_t len)
+static void zr5_hash_512(const char* input, char* output, uint32_t len)
 {
 	sph_keccak512_context ctx_keccak;
 	sph_blake512_context ctx_blake;
@@ -65,15 +66,16 @@ void zr5_hash(const char* input, char* output, uint32_t len)
 	unsigned int norder = hash[0][0] % ARRAY_SIZE(permut); /* % 24 */
 	int i;
 
+#ifdef TEST_VERBOSELY
 	for(i=0; i<len; i++) printf("%02x", (unsigned char)input[i]); printf("\n");
 	for(i=0; i<32; i++) printf("%02x", (unsigned char)ph[i]); printf("\n");
-
+#endif
 	for(i = 0; i < 4; i++)
 	{
 		void* phash = (void*) &(hash[i][0]);
 		void* pdest = (void*) &(hash[i+1][0]);
 
-		printf("permut %d\n", permut[norder][i]);
+		//printf("permut %d\n", permut[norder][i]);
 		switch (permut[norder][i]) {
 		case ZR_BLAKE:
 			sph_blake512_init(&ctx_blake);
@@ -102,3 +104,72 @@ void zr5_hash(const char* input, char* output, uint32_t len)
 	memcpy(output, &hash[4], 32);
 }
 
+
+void zr5_hash(const char* input, char* output, uint32_t len)
+{
+        uint8_t *input512;      // writeable copy of input
+        uint8_t output512[64];  // output of both zr5 hashes
+        uint32_t version;       // writeable copy of version
+        uint32_t nPoK = 0;      // integer copy of PoK state
+#ifdef TEST_VERBOSELY
+        char buffer[512] = { 0 };
+        char *buf = buffer;
+        uint32_t i = 0;
+#endif
+
+        // copy the input buffer at input to a modifiable location at input512,
+        input512 = (uint8_t*)malloc(len);               // allocate space for the copy
+        memcpy((uint8_t*)input512, (uint8_t*)input, len);
+
+#ifdef TEST_VERBOSELY
+        fprintf(stderr, "zr5 input: ");
+        for (i=0; i<len; i++) sprintf(stderr, "%02x", input512[i]);
+        fprintf(stderr, "\n");
+#endif
+
+        // store the version bytes
+        memcpy((uint8_t *)&version, (uint8_t *)input, 4);
+
+        // apply the first hash, yielding 512bits = 64 bytes
+        zr5_hash_512(input512, output512, len);
+
+        // Now begins Proof of Knowledge
+        //
+        // Pull the data from the result for the Proof of Knowledge
+        // (this is the 3rd and 4th of the first four bytes of the result)
+        memcpy(&nPoK, (uint8_t *)output512, 4); // yields big or little endian uint
+        // keep only the two least significant bytes
+#if BYTE_ORDER == LITTLE_ENDIAN
+        nPoK &= 0xFFFF0000;             // bytes 3&4 of big endian are 1&2 of little endian
+#else
+        nPoK &= 0x0000FFFF;             // bytes 1&2 of big endian are 3&4 of little endian
+#endif
+        //
+        // PoK part 2:
+        // update the version variable with the masks and PoK value
+        // according to the Proof of Knowledge setting
+        version &= (~POK_BOOL_MASK);
+        version |= (POK_DATA_MASK & nPoK);
+#ifdef TEST_VERBOSELY
+        fprintf(stderr, "new version field: %x\n", version);
+#endif
+
+        // and now write it back out to our copy of the input buffer
+        memcpy((uint8_t *)input512, (uint8_t *)&version, 4);
+
+        // apply a second ZR5 hash of the modified input, 512 bits in and out,
+        // to the input modified with PoK. Length is still the original length
+        zr5_hash_512(input512, output512, len);
+
+        // copy the left-most 256 bits (32 bytes) of the last hash into the output buffer
+        memcpy((uint8_t *)output, (uint8_t *)output512, sizeof(output512)/2);
+
+#ifdef TEST_VERBOSELY
+        buf += sprintf(buf, "zr5 hash: ");
+        for (i=0; i<32; i++) { buf += sprintf(buf, "%02x", output512[i]); }
+        fprintf(stderr, "%s\n", buffer); buf = buffer;
+#endif
+
+        free(input512);
+        return;
+}
diff --git a/stratum/client_submit.cpp b/stratum/client_submit.cpp
index 82fce82..9ed2ceb 100644
--- a/stratum/client_submit.cpp
+++ b/stratum/client_submit.cpp
@@ -263,7 +263,8 @@ bool client_submit(YAAMP_CLIENT *client, json_value *json_params)
 	memset(&submitvalues, 0, sizeof(submitvalues));
 
 	build_submit_values(&submitvalues, templ, client->extranonce1, extranonce2, ntime, nonce);
-	if(submitvalues.hash_bin[30] || submitvalues.hash_bin[31])
+	// zr5 has data here, ignore it... reversed endian ?
+	if((submitvalues.hash_bin[30] || submitvalues.hash_bin[31]) && g_current_algo && strcmp(g_current_algo->name, "zr5"))
 	{
 		client_submit_error(client, job, 25, "Invalid share", extranonce2, ntime, nonce);
 		return true;