diff --git a/include/ftxui/screen/screen.hpp b/include/ftxui/screen/screen.hpp
index 5120472..9e609b6 100644
--- a/include/ftxui/screen/screen.hpp
+++ b/include/ftxui/screen/screen.hpp
@@ -62,8 +62,8 @@ class Screen {
   void Print();
 
   // Get screen dimensions.
-  int dimx() { return dimx_; }
-  int dimy() { return dimy_; }
+  int dimx() const { return dimx_; }
+  int dimy() const { return dimy_; }
 
   // Move the terminal cursor n-lines up with n = dimy().
   std::string ResetPosition(bool clear = false);
diff --git a/include/ftxui/util/ref.hpp b/include/ftxui/util/ref.hpp
index 2eb7eb5..ff1133a 100644
--- a/include/ftxui/util/ref.hpp
+++ b/include/ftxui/util/ref.hpp
@@ -13,9 +13,9 @@ class ConstRef {
   ConstRef() {}
   ConstRef(T t) : owned_(t) {}
   ConstRef(const T* t) : address_(t) {}
-  const T& operator*() { return address_ ? *address_ : owned_; }
-  const T& operator()() { return address_ ? *address_ : owned_; }
-  const T* operator->() { return address_ ? address_ : &owned_; }
+  const T& operator*() const { return address_ ? *address_ : owned_; }
+  const T& operator()() const { return address_ ? *address_ : owned_; }
+  const T* operator->() const { return address_ ? address_ : &owned_; }
 
  private:
   T owned_;
@@ -82,8 +82,10 @@ class ConstStringRef {
   ConstStringRef(const wchar_t* ref) : ConstStringRef(std::wstring(ref)) {}
   ConstStringRef(const char* ref)
       : ConstStringRef(to_wstring(std::string(ref))) {}
-  const std::string& operator*() { return address_ ? *address_ : owned_; }
-  const std::string* operator->() { return address_ ? address_ : &owned_; }
+  const std::string& operator*() const { return address_ ? *address_ : owned_; }
+  const std::string* operator->() const {
+    return address_ ? address_ : &owned_;
+  }
 
  private:
   const std::string owned_;