diff --git a/src/tools/ranges/ViewBase.hpp b/src/tools/ranges/ViewBase.hpp
index 63224d9..f0f65e3 100644
--- a/src/tools/ranges/ViewBase.hpp
+++ b/src/tools/ranges/ViewBase.hpp
@@ -2,6 +2,7 @@
 #define NJOY_TOOLS_RANGES_VIEWBASE
 
 // system includes
+#include <cassert>
 #include <stdexcept>
 
 // other includes
@@ -45,6 +46,7 @@ class ViewBase {
                                  typename Range::iterator > = true >
   constexpr decltype(auto) front() const noexcept {
 
+    assert( ( !this->empty(), "front(): view is empty" ) );
     return *( this->derived().begin() );
   }
 
@@ -56,6 +58,7 @@ class ViewBase {
                                  typename Range::iterator > = true >
   constexpr decltype(auto) back() const noexcept {
 
+    assert( ( !this->empty(), "back(): view is empty" ) );
     return *( std::prev( this->derived().end() ) );
   }