diff --git a/containers/named_array.c b/containers/named_array.c
index 7cbd484..3aac6b5 100644
--- a/containers/named_array.c
+++ b/containers/named_array.c
@@ -61,7 +61,7 @@ void* named_array_alloc(NamedArray* array, unsigned int* new_id) {
 void* named_array_reserve(NamedArray* array, unsigned int id) {
     if(!named_array_used(array, id)) {
         unsigned int j = (id % 8) - 1;
-        unsigned int i = (id - j) / 8;
+        unsigned int i = id / 8;
 
         assert(!named_array_used(array, id));
         array->used_markers[i] |= (unsigned char) 1 << j;