diff --git a/include/gsl/assert b/include/gsl/assert
index b5d2669..5488122 100644
--- a/include/gsl/assert
+++ b/include/gsl/assert
@@ -109,14 +109,14 @@ public:
     using handler = void (*)();
 #endif
 
-    contract_group  (handler h)            { set_handler(h); }
-    auto set_handler(handler h) -> handler { return std::exchange(chandler, h ? h : []()noexcept{}); }
-    auto get_handler()          -> handler { return chandler; }
+    constexpr contract_group  (handler h)            { set_handler(h); }
+    constexpr auto set_handler(handler h) -> handler { return std::exchange(chandler, h ? h : []()noexcept{}); }
+    constexpr auto get_handler()          -> handler { return chandler; }
 
-    void expects  (bool b) { assertion(b); }
-    void ensures  (bool b) { assertion(b); }
+    constexpr void expects  (bool b) { assertion(b); }
+    constexpr void ensures  (bool b) { assertion(b); }
 private:
-    void assertion(bool b) { if (!b) chandler(); }
+    constexpr void assertion(bool b) { if (!b) chandler(); }
     handler chandler;
 };