diff --git a/iguana/exchanges/LP_bitcoin.c b/iguana/exchanges/LP_bitcoin.c
index 80f6a3813..4a3830093 100644
--- a/iguana/exchanges/LP_bitcoin.c
+++ b/iguana/exchanges/LP_bitcoin.c
@@ -3494,8 +3494,13 @@ bits256 bitcoin_sigtxid(char *symbol,uint8_t taddr,uint8_t pubtype,uint8_t p2sht
         memcpy(&for_sig_hash[len], sequence_hash, 32);
         len += 32;
 
-        uint8_t outputs[1000], hash_outputs[32];
+        uint8_t *outputs, hash_outputs[32];
         int32_t outputs_len = 0;
+        for (i = 0; i < dest.tx_out; i++) { // calc size for outputs buffer
+            outputs_len += sizeof(dest.vouts[i].value); outputs_len++;  outputs_len += dest.vouts[i].pk_scriptlen;
+        }
+        outputs = malloc(outputs_len);
+        outputs_len = 0;
         for (i = 0; i < dest.tx_out; i++) {
             outputs_len += iguana_rwnum(1, &outputs[outputs_len], sizeof(dest.vouts[i].value), &dest.vouts[i].value);
             outputs[outputs_len++] = (uint8_t) dest.vouts[i].pk_scriptlen;
@@ -3516,6 +3521,8 @@ bits256 bitcoin_sigtxid(char *symbol,uint8_t taddr,uint8_t pubtype,uint8_t p2sht
         memcpy(&for_sig_hash[len], hash_outputs, 32);
         len += 32;
 
+        free(outputs);
+
         // no join splits, fill the hashJoinSplits with 32 zeros
         memset(&for_sig_hash[len], 0, 32);
         len += 32;