diff --git a/lib/Sema/CSApply.cpp b/lib/Sema/CSApply.cpp
index c4baa20e0ca..ce62c8706a7 100644
--- a/lib/Sema/CSApply.cpp
+++ b/lib/Sema/CSApply.cpp
@@ -5399,7 +5399,8 @@ Expr *ExprRewriter::coerceCallArguments(Expr *arg, AnyFunctionType *funcType,
 
       // Otherwise, create a call of the default argument generator.
       } else {
-        const ParamDecl *defaultParam = getParameterAt(cast<ValueDecl>(callee.getDecl()), newArgs.size());
+        const ParamDecl *defaultParam = getParameterAt(callee.getDecl(),
+                                                       newArgs.size());
         defArg = defaultParam->getDefaultValue();
 
         if (defArg == nullptr) {
diff --git a/test/SILGen/keypaths.swift b/test/SILGen/keypaths.swift
index bea888ba744..2c4cf966dce 100644
--- a/test/SILGen/keypaths.swift
+++ b/test/SILGen/keypaths.swift
@@ -397,7 +397,10 @@ func subscripts<T: Hashable, U: Hashable>(x: T, y: U, s: String) {
   _ = \SubscriptDefaults1.[bool: false, 0, 0]
   
   _ = \SubscriptDefaults2.[]
+  _ = \SubscriptDefaults2.[0]
+  
   _ = \SubscriptDefaults3.[]
+  _ = \SubscriptDefaults3.[0]
 }
 
 // CHECK-LABEL: sil hidden [ossa] @{{.*}}subclass_generics