diff --git a/src/ddmd/traits.d b/src/ddmd/traits.d
index a2d5979fc2dd..3c1cdf0d7fb7 100644
--- a/src/ddmd/traits.d
+++ b/src/ddmd/traits.d
@@ -1021,9 +1021,9 @@ extern (C++) Expression semanticTraits(TraitsExp e, Scope* sc)
         }
         ex = ex.ctfeInterpret();
         auto ii = ex.toUInteger();
-        if (ii >= fparams.dim)
+        if (ii >= Parameter.dim(fparams))
         {
-            e.error("parameter index must be in range 0..%u not %s", cast(uint)fparams.dim, ex.toChars());
+            e.error("parameter index must be in range 0..%u not %s", cast(uint)Parameter.dim(fparams), ex.toChars());
             return new ErrorExp();
         }
 
diff --git a/test/runnable/traits.d b/test/runnable/traits.d
index d6f301d4088a..ef23e9f32bef 100644
--- a/test/runnable/traits.d
+++ b/test/runnable/traits.d
@@ -1514,6 +1514,19 @@ void test12237()
 
 /********************************************************/
 
+void async(ARGS...)(ARGS)
+{
+        static void compute(ARGS)
+        {
+        }
+
+        auto x = __traits(getParameterStorageClasses, compute, 1);
+}
+
+alias test17495 = async!(int, int);
+
+/********************************************************/
+
 int main()
 {
     test1();