diff --git a/include/boost/static_string/static_string.hpp b/include/boost/static_string/static_string.hpp
index 9a73c93..b7df809 100644
--- a/include/boost/static_string/static_string.hpp
+++ b/include/boost/static_string/static_string.hpp
@@ -289,14 +289,14 @@ public:
 
   BOOST_STATIC_STRING_CPP11_CONSTEXPR
   std::size_t
-  set_size(std::size_t) noexcept
+  set_size(std::size_t) const noexcept
   {
     return 0;
   }
 
   BOOST_STATIC_STRING_CPP14_CONSTEXPR
   void
-  term_impl() noexcept { }
+  term_impl() const noexcept { }
 
 private:
   static constexpr const value_type null_{};
diff --git a/test/constexpr_tests.hpp b/test/constexpr_tests.hpp
index 5b249f5..5e5fa24 100644
--- a/test/constexpr_tests.hpp
+++ b/test/constexpr_tests.hpp
@@ -54,6 +54,7 @@ testConstantEvaluation()
   //cstatic_string g(f.begin(), f.end());
   cstatic_string h(f);
   cstatic_string i({'a'});
+  static_cast<void>((c, d, e, f, h, i));
 
   // assignment
   a = b;
@@ -102,7 +103,8 @@ testConstantEvaluation()
 
   // capacity and size
   cstatic_string().size();
-  cstatic_string().empty();
+  // this is potentially marked nodiscard
+  static_cast<void>(cstatic_string().empty());
   cstatic_string().length();
   cstatic_string().max_size();
   cstatic_string().capacity();
@@ -228,6 +230,7 @@ testConstantEvaluation()
   //cstatic_string g(f.begin(), f.end());
   cstatic_string h(f);
   cstatic_string i({'a'});
+  static_cast<void>((c, d, e, f, h, i));
 
   // assignment
   a = b;
@@ -284,7 +287,8 @@ testConstantEvaluation()
 
   // capacity and size
   cstatic_string().size();
-  cstatic_string().empty();
+  // this is potentially marked nodiscard
+  static_cast<void>(cstatic_string().empty());
   cstatic_string().length();
   cstatic_string().max_size();
   cstatic_string().capacity();
@@ -410,6 +414,7 @@ testConstantEvaluation()
   //cstatic_string g(f.begin(), f.end());
   cstatic_string h(f);
   cstatic_string i({'a'});
+  static_cast<void>((c, d, e, f, h, i));
 
   // assignment
   a = b;
@@ -452,7 +457,8 @@ testConstantEvaluation()
 
   // capacity and size
   cstatic_string().size();
-  cstatic_string().empty();
+  // this is potentially marked nodiscard
+  static_cast<void>(cstatic_string().empty());
   cstatic_string().length();
   cstatic_string().max_size();
   cstatic_string().capacity();
diff --git a/test/static_string.cpp b/test/static_string.cpp
index 14a0ea7..119b9ef 100644
--- a/test/static_string.cpp
+++ b/test/static_string.cpp
@@ -7036,8 +7036,8 @@ testEmpty()
 {
   static_string<0> a;
   BOOST_TEST(a.size() == 0);
-  BOOST_TEST(a.data());
-  BOOST_TEST(!a.capacity());
+  BOOST_TEST(a.data() != nullptr);
+  BOOST_TEST(a.capacity() == 0);
 }
 
 void