diff --git a/src/cdrizzleapi.c b/src/cdrizzleapi.c
index f24b132..6cf2e88 100644
--- a/src/cdrizzleapi.c
+++ b/src/cdrizzleapi.c
@@ -59,8 +59,6 @@ process_array_list(PyObject *list, integer_t *nx, integer_t *ny,
     PyArrayObject *arr = NULL;
     int i, at_least_one;
 
-    // *nx = -1;
-    // *ny = -1;
     *arrays = NULL;
     *nmax = 0;
     if (n_none) {
@@ -93,6 +91,13 @@ process_array_list(PyObject *list, integer_t *nx, integer_t *ny,
         *nx = (int)ndim[1];
         *ny = (int)ndim[0];
         *arrays = arr_list;
+        for (int i = 0; i < (*nmax); ++i) {
+            if (!(*arrays)[i]) {
+                driz_error_set(error, PyExc_ValueError,
+                               "Some of the 'out2_list' arrays are NULL!");
+                goto _exit_on_err;
+            }
+        }
         return 0;
 
     } else if (!PyList_Check(list) && !PyTuple_Check(list)) {