diff --git a/src/bitcoin.c b/src/bitcoin.c
index 71c576f0..272dd2a0 100644
--- a/src/bitcoin.c
+++ b/src/bitcoin.c
@@ -83,7 +83,6 @@ out:
 static bool gbt_merkle_bins(gbtbase_t *gbt, json_t *transaction_arr)
 {
 	int i, j, binleft, binlen;
-	char hashhex[68];
 	json_t *arr_val;
 	uchar *hashbin;
 
@@ -147,7 +146,7 @@ static bool gbt_merkle_bins(gbtbase_t *gbt, json_t *transaction_arr)
 		while (42) {
 			if (binleft == 1)
 				break;
-			memcpy(gbt->merklebin + (gbt->merkles * 32), hashbin + 32, 32);
+			memcpy(&gbt->merklebin[gbt->merkles][0], hashbin + 32, 32);
 			gbt->merkles++;
 			if (binleft % 2) {
 				memcpy(hashbin + binlen, hashbin + binlen - 32, 32);
@@ -161,8 +160,8 @@ static bool gbt_merkle_bins(gbtbase_t *gbt, json_t *transaction_arr)
 		}
 	}
 	for (i = 0; i < gbt->merkles; i++) {
-		__bin2hex(hashhex, gbt->merklebin + i * 32, 32);
-		LOGDEBUG("MH%d %s",i, hashhex);
+		__bin2hex(&gbt->merklehash[i][0], &gbt->merklebin[i][0], 32);
+		LOGDEBUG("MH%d %s",i, &gbt->merklehash[i][0]);
 	}
 	LOGINFO("Stored %d transactions", gbt->transactions);
 	return true;
diff --git a/src/libckpool.h b/src/libckpool.h
index c1f30e54..e4615256 100644
--- a/src/libckpool.h
+++ b/src/libckpool.h
@@ -120,7 +120,8 @@ struct gbtbase {
 	uchar *txn_hashes;
 	int transactions;
 	int merkles;
-	uchar merklebin[16 * 32];
+	uchar merklebin[16][32];
+	char merklehash[16][68];
 };
 
 typedef struct gbtbase gbtbase_t;