diff --git a/libs/util/include/psemek/util/spatial_array.hpp b/libs/util/include/psemek/util/spatial_array.hpp
index eec15f10..3f2df07c 100644
--- a/libs/util/include/psemek/util/spatial_array.hpp
+++ b/libs/util/include/psemek/util/spatial_array.hpp
@@ -50,6 +50,8 @@ namespace psemek::util
 	template <typename ... Ix>
 	T & spatial_array<T, N, Index>::get(Ix ... index)
 	{
+		static_assert(sizeof...(Ix) == N, "wrong number of indices");
+
 		if (!contains(index...))
 			expand(index...);
 
@@ -63,6 +65,8 @@ namespace psemek::util
 	template <typename ... Ix>
 	T * spatial_array<T, N, Index>::get_if(Ix ... index)
 	{
+		static_assert(sizeof...(Ix) == N, "wrong number of indices");
+
 		if (!contains(index...))
 			return nullptr;
 
@@ -76,6 +80,8 @@ namespace psemek::util
 	template <typename ... Ix>
 	T const * spatial_array<T, N, Index>::get_if(Ix ... index) const
 	{
+		static_assert(sizeof...(Ix) == N, "wrong number of indices");
+
 		if (!contains(index...))
 			return nullptr;
 
@@ -89,6 +95,8 @@ namespace psemek::util
 	template <typename ... Ix>
 	T const & spatial_array<T, N, Index>::at(Ix ... index) const
 	{
+		static_assert(sizeof...(Ix) == N, "wrong number of indices");
+
 		auto const size = array_.dims();
 		Index ix[N] {index...};
 		for (std::size_t i = 0; i < N; ++i)
@@ -104,6 +112,8 @@ namespace psemek::util
 	template <typename ... Ix>
 	bool spatial_array<T, N, Index>::contains(Ix ... index) const
 	{
+		static_assert(sizeof...(Ix) == N, "wrong number of indices");
+
 		auto const size = array_.dims();
 		Index ix[N] {index...};
 		for (std::size_t i = 0; i < N; ++i)
@@ -116,6 +126,8 @@ namespace psemek::util
 	template <typename ... Ix>
 	void spatial_array<T, N, Index>::expand(Ix ... index)
 	{
+		static_assert(sizeof...(Ix) == N, "wrong number of indices");
+
 		Index ix[N] {index...};
 
 		if (array_.empty())