diff --git a/bip-0075/paymentrequest.proto b/bip-0075/paymentrequest.proto
index d1c9e4f2..1c9cc8e9 100644
--- a/bip-0075/paymentrequest.proto
+++ b/bip-0075/paymentrequest.proto
@@ -45,7 +45,7 @@ message Payment {
 }
 message PaymentACK {
         required Payment payment = 1;      // Payment message that triggered this ACK
-        optional string memo = 2;          // human-readable message for customer
+        optional string memo = 2;          // Human-readable message for customer
 }
 
 // BIP-IR Extensions