diff --git a/src/analysis/unused.d b/src/analysis/unused.d
index ad20543..033fa82 100644
--- a/src/analysis/unused.d
+++ b/src/analysis/unused.d
@@ -299,18 +299,15 @@ class UnusedVariableCheck : BaseAnalyzer
 
 	override void visit(const Parameter parameter)
 	{
-		import std.algorithm : canFind;
+		import std.algorithm : among;
 		import std.algorithm.iteration : filter;
 		import std.range : empty;
 		import std.array : array;
 
 		if (parameter.name != tok!"")
 		{
-			immutable bool isRef =
-				canFind(parameter.parameterAttributes, cast(IdType) tok!"ref") ||
-				canFind(parameter.parameterAttributes, cast(IdType) tok!"in") ||
-				canFind(parameter.parameterAttributes, cast(IdType) tok!"out");
-
+			immutable bool isRef = !parameter.parameterAttributes
+				.filter!(a => a.among(tok!"ref", tok!"out")).empty;
 			immutable bool isPtr = parameter.type && !parameter.type
 				.typeSuffixes.filter!(a => a.star != tok!"").empty;
 
@@ -461,6 +458,8 @@ private:
 		int a; // [warn]: Variable a is never used.
 	}
 
+	void inPSC(in int a){} // [warn]: Parameter a is never used.
+
 	// Issue 380
 	int templatedEnum()
 	{