diff --git a/clang/lib/AST/ByteCode/InterpBuiltin.cpp b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
index b788656f9484fc..85cffb0c4332df 100644
--- a/clang/lib/AST/ByteCode/InterpBuiltin.cpp
+++ b/clang/lib/AST/ByteCode/InterpBuiltin.cpp
@@ -243,7 +243,7 @@ static bool interp__builtin_strlen(InterpState &S, CodePtr OpPC,
   unsigned ID = Func->getBuiltinID();
   const Pointer &StrPtr = getParam<Pointer>(Frame, 0);
 
-  if (ID == Builtin::BIstrlen || ID == Builtin::BIwcslen)
+  if (ID == Builtin::BIstrlen)
     diagnoseNonConstexprBuiltin(S, OpPC, ID);
 
   if (!CheckArray(S, OpPC, StrPtr))
@@ -1859,8 +1859,6 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
     break;
   case Builtin::BI__builtin_strlen:
   case Builtin::BIstrlen:
-  case Builtin::BI__builtin_wcslen:
-  case Builtin::BIwcslen:
     if (!interp__builtin_strlen(S, OpPC, Frame, F, Call))
       return false;
     break;
diff --git a/clang/test/AST/ByteCode/builtin-functions.cpp b/clang/test/AST/ByteCode/builtin-functions.cpp
index b951c04dde5980..f70b77fe74636b 100644
--- a/clang/test/AST/ByteCode/builtin-functions.cpp
+++ b/clang/test/AST/ByteCode/builtin-functions.cpp
@@ -15,10 +15,6 @@
 #error "huh?"
 #endif
 
-extern "C" {
-  typedef decltype(sizeof(int)) size_t;
-  extern size_t wcslen(const wchar_t *p);
-}
 
 namespace strcmp {
   constexpr char kFoobar[6] = {'f','o','o','b','a','r'};
@@ -97,14 +93,6 @@ constexpr const char *a = "foo\0quux";
   constexpr char d[] = { 'f', 'o', 'o' }; // no nul terminator.
   constexpr int bad = __builtin_strlen(d); // both-error {{constant expression}} \
                                            // both-note {{one-past-the-end}}
-
-  constexpr int wn = __builtin_wcslen(L"hello");
-  static_assert(wn == 5);
-  constexpr int wm = wcslen(L"hello"); // both-error {{constant expression}} \
-                                       // both-note {{non-constexpr function 'wcslen' cannot be used in a constant expression}}
-
-  int arr[3]; // both-note {{here}}
-  int wk = arr[wcslen(L"hello")]; // both-warning {{array index 5}}
 }
 
 namespace nan {