diff --git a/src/paymentdisclosure.h b/src/paymentdisclosure.h
index e6a995ab4..c5d29d5c6 100644
--- a/src/paymentdisclosure.h
+++ b/src/paymentdisclosure.h
@@ -73,7 +73,7 @@ struct PaymentDisclosurePayload {
     uint8_t version;        // 0 = experimental, 1 = first production version, etc.
     uint256 esk;            // zcash/NoteEncryption.cpp
     uint256 txid;           // primitives/transaction.h
-    size_t js;              // Index into CTransaction.vjoinsplit
+    uint64_t js;            // Index into CTransaction.vjoinsplit
     uint8_t n;              // Index into JSDescription fields of length ZC_NUM_JS_OUTPUTS
     libzcash::PaymentAddress zaddr; // zcash/Address.hpp
     std::string message;     // parameter to RPC call
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 82fb1dca0..cfa0cbf8b 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -159,7 +159,7 @@ public:
     // Transaction hash
     uint256 hash;
     // Index into CTransaction.vjoinsplit
-    size_t js;
+    uint64_t js;
     // Index into JSDescription fields of length ZC_NUM_JS_OUTPUTS
     uint8_t n;