diff --git a/doc/release-notes.md b/doc/release-notes.md
index 3562ae590..d44a87f81 100644
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -45,7 +45,8 @@ Changes to Block Template Construction
 - The block template construction algorithm no longer favours transactions that
   were previously considered "high priority" because they spent older inputs. The
   `-blockprioritysize` config option, which configured the portion of the block
-  reserved for these transactions, has been removed and is now ignored.
+  reserved for these transactions, has been removed and will now cause a warning
+  if used.
 
 Removal of Priority Estimation
 ------------------------------
diff --git a/src/init.cpp b/src/init.cpp
index 70634bbd4..c218922c0 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1295,6 +1295,10 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     }
 #endif
 
+    if (GetArg("-blockprioritysize", 0) != 0) {
+        InitWarning(_("The argument -blockprioritysize is no longer supported."));
+    }
+
     if (!mapMultiArgs["-nuparams"].empty()) {
         // Allow overriding network upgrade parameters for testing
         if (chainparams.NetworkIDString() != "regtest") {