diff --git a/clang/lib/AST/Interp/InterpStack.h b/clang/lib/AST/Interp/InterpStack.h
index 435120d0e4414..fa2f9d5b242de 100644
--- a/clang/lib/AST/Interp/InterpStack.h
+++ b/clang/lib/AST/Interp/InterpStack.h
@@ -44,7 +44,7 @@ class InterpStack final {
     assert(ItemTypes.back() == toPrimType<T>());
     ItemTypes.pop_back();
 #endif
-    auto *Ptr = &peek<T>();
+    auto *Ptr = &peekInternal<T>();
     auto Value = std::move(*Ptr);
     Ptr->~T();
     shrink(aligned_size<T>());
@@ -57,14 +57,18 @@ class InterpStack final {
     assert(ItemTypes.back() == toPrimType<T>());
     ItemTypes.pop_back();
 #endif
-    auto *Ptr = &peek<T>();
+    auto *Ptr = &peekInternal<T>();
     Ptr->~T();
     shrink(aligned_size<T>());
   }
 
   /// Returns a reference to the value on the top of the stack.
   template <typename T> T &peek() const {
-    return *reinterpret_cast<T *>(peekData(aligned_size<T>()));
+#ifndef NDEBUG
+    assert(!ItemTypes.empty());
+    assert(ItemTypes.back() == toPrimType<T>());
+#endif
+    return peekInternal<T>();
   }
 
   template <typename T> T &peek(size_t Offset) const {
@@ -92,6 +96,11 @@ class InterpStack final {
     return ((sizeof(T) + PtrAlign - 1) / PtrAlign) * PtrAlign;
   }
 
+  /// Like the public peek(), but without the debug type checks.
+  template <typename T> T &peekInternal() const {
+    return *reinterpret_cast<T *>(peekData(aligned_size<T>()));
+  }
+
   /// Grows the stack to accommodate a value and returns a pointer to it.
   void *grow(size_t Size);
   /// Returns a pointer from the top of the stack.