diff --git a/src/Var.cc b/src/Var.cc
index baa4c0dae7..0b19d389e2 100644
--- a/src/Var.cc
+++ b/src/Var.cc
@@ -450,7 +450,15 @@ static std::optional<zeek::FuncType::Prototype> func_type_check(const zeek::Func
 		return {};
 		}
 
-	return decl->FindPrototype(*impl->Params());
+	auto rval = decl->FindPrototype(*impl->Params());
+
+	if ( rval )
+		for ( auto i = 0; i < rval->args->NumFields(); ++i )
+			if ( rval->args->FieldDecl(i)->GetAttr(zeek::detail::ATTR_DEPRECATED) )
+				impl->Warn(fmt("use of deprecated parameter '%s'",
+				               rval->args->FieldName(i)), decl, true);
+
+	return rval;
 	}
 
 static bool canonical_arg_types_match(const zeek::FuncType* decl, const zeek::FuncType* impl)
diff --git a/testing/btest/Baseline/language.alternate-prototypes-deprecated-args/out b/testing/btest/Baseline/language.alternate-prototypes-deprecated-args/out
new file mode 100644
index 0000000000..8acfd27bf5
--- /dev/null
+++ b/testing/btest/Baseline/language.alternate-prototypes-deprecated-args/out
@@ -0,0 +1,5 @@
+warning in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 9 and /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 5: use of deprecated parameter 'b' (event(a:string; b:string; c:string;))
+warning in /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 19 and /home/jon/pro/zeek/zeek/testing/btest/.tmp/language.alternate-prototypes-deprecated-args/alternate-prototypes-deprecated-args.zeek, line 5: use of deprecated prototype (event(a:string; b:string;) and myev)
+myev (canon), one, two, three
+myev (new), one, three
+myev (old), one, two
diff --git a/testing/btest/language/alternate-prototypes-deprecated-args.zeek b/testing/btest/language/alternate-prototypes-deprecated-args.zeek
new file mode 100644
index 0000000000..659c4c7a16
--- /dev/null
+++ b/testing/btest/language/alternate-prototypes-deprecated-args.zeek
@@ -0,0 +1,28 @@
+# @TEST-EXEC: zeek -b %INPUT >out 2>&1
+#
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff out
+
+global myev: event(a: string, b: string &deprecated="Don't use 'b'", c: string);
+global myev: event(a: string, c: string);
+global myev: event(a: string, b: string) &deprecated="Don't use this prototype";
+
+event myev(a: string, b: string, c: string) &priority=11
+	{
+	print "myev (canon)", a, b, c;
+	}
+
+event myev(a: string, c: string) &priority = 7
+	{
+	print "myev (new)", a, c;
+	}
+
+event myev(a: string, b: string) &priority = 5
+	{
+	print "myev (old)", a, b;
+	}
+
+event zeek_init()
+	{
+	event myev("one", "two", "three");
+	}
+