diff --git a/src/coins.h b/src/coins.h
index dc34309798..e7995f9641 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -72,6 +72,9 @@ public:
         ::Unserialize(s, Using<TxOutCompression>(out));
     }
 
+    /** Either this coin never existed (see e.g. coinEmpty in coins.cpp), or it
+      * did exist and has been spent.
+      */
     bool IsSpent() const {
         return out.IsNull();
     }