diff --git a/tpie/internal_stack.h b/tpie/internal_stack.h
index 6084f61d3..c63bca950 100644
--- a/tpie/internal_stack.h
+++ b/tpie/internal_stack.h
@@ -54,6 +54,8 @@ class internal_stack: public internal_stack_vector_base<T,internal_stack<T> > {
 
 	///////////////////////////////////////////////////////////////////////////
 	/// \brief Add an element to the top of the stack.
+	/// If size() is equal to the capacity (set in the constructor or in
+	/// resize()), effects are undefined. resize() is not called implicitly.
 	///
 	/// \param val The element to add.
 	///////////////////////////////////////////////////////////////////////////
diff --git a/tpie/internal_vector.h b/tpie/internal_vector.h
index 7b90204c6..ef2edba02 100644
--- a/tpie/internal_vector.h
+++ b/tpie/internal_vector.h
@@ -80,6 +80,8 @@ class internal_vector: public internal_stack_vector_base<T,internal_vector<T> >
 
 	///////////////////////////////////////////////////////////////////////////
 	/// \brief Add an element to the end of the vector.
+	/// If size() is equal to the capacity (set in the constructor or in
+	/// resize()), effects are undefined. resize() is not called implicitly.
 	///
 	/// Iterators are invalidated by this call.
 	///