diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -4080,9 +4080,10 @@
 
 /// getExtVectorType - Return the unique reference to an extended vector type of
 /// the specified element type and size. VectorType must be a built-in type.
-QualType
-ASTContext::getExtVectorType(QualType vecType, unsigned NumElts) const {
-  assert(vecType->isBuiltinType() || vecType->isDependentType());
+QualType ASTContext::getExtVectorType(QualType vecType,
+                                      unsigned NumElts) const {
+  assert(vecType->isBuiltinType() || vecType->isDependentType() ||
+         vecType->isBitIntType());
 
   // Check if we've already instantiated a vector of this type.
   llvm::FoldingSetNodeID ID;
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -2707,7 +2707,7 @@
   // We explictly allow bool elements in ext_vector_type for C/C++.
   bool IsNoBoolVecLang = getLangOpts().OpenCL || getLangOpts().OpenCLCPlusPlus;
   if ((!T->isDependentType() && !T->isIntegerType() &&
-       !T->isRealFloatingType()) || T->isBitIntType() ||
+       !T->isRealFloatingType()) ||
       (IsNoBoolVecLang && T->isBooleanType())) {
     Diag(AttrLoc, diag::err_attribute_invalid_vector_type) << T;
     return QualType();
diff --git a/clang/test/Sema/builtin-classify-type.c b/clang/test/Sema/builtin-classify-type.c
--- a/clang/test/Sema/builtin-classify-type.c
+++ b/clang/test/Sema/builtin-classify-type.c
@@ -29,6 +29,8 @@
   __attribute__((vector_size(16))) int vec;
   typedef __attribute__((ext_vector_type(4))) int evec_t;
   evec_t evec;
+  typedef _BitInt(16) int16_t3 __attribute__((ext_vector_type(3)));
+  int16_t3 t3;
   _Atomic int atomic_i;
   _Atomic double atomic_d;
   _Complex int complex_i;
diff --git a/clang/test/SemaCXX/ext-int.cpp b/clang/test/SemaCXX/ext-int.cpp
--- a/clang/test/SemaCXX/ext-int.cpp
+++ b/clang/test/SemaCXX/ext-int.cpp
@@ -83,11 +83,6 @@
   static constexpr bool value = true;
 };
 
-// Reject vector types:
-// expected-error@+1{{invalid vector element type '_BitInt(32)'}}
-typedef _BitInt(32) __attribute__((vector_size(16))) VecTy;
-// expected-error@+1{{invalid vector element type '_BitInt(32)'}}
-typedef _BitInt(32) __attribute__((ext_vector_type(32))) OtherVecTy;
 
 // Allow _Complex:
 _Complex _BitInt(3) Cmplx;