diff --git a/numpy/core/include/numpy/ndarraytypes.h b/numpy/core/include/numpy/ndarraytypes.h
index 19bbc7435..ecab1d52a 100644
--- a/numpy/core/include/numpy/ndarraytypes.h
+++ b/numpy/core/include/numpy/ndarraytypes.h
@@ -252,7 +252,8 @@ typedef enum {
         NPY_FR_ps = 11,/* picoseconds */
         NPY_FR_fs = 12,/* femtoseconds */
         NPY_FR_as = 13,/* attoseconds */
-        NPY_FR_GENERIC = 14 /* Generic, unbound units, can convert to anything */
+        NPY_FR_GENERIC = 14, /* Generic, unbound units, can convert to anything */
+        NPY_DATETIMEUNIT_NULL = -1
 } NPY_DATETIMEUNIT;
 
 /*
diff --git a/numpy/core/src/multiarray/datetime_strings.c b/numpy/core/src/multiarray/datetime_strings.c
index b9aeda508..263ef96a1 100644
--- a/numpy/core/src/multiarray/datetime_strings.c
+++ b/numpy/core/src/multiarray/datetime_strings.c
@@ -795,6 +795,8 @@ get_datetime_iso_8601_strlen(int local, NPY_DATETIMEUNIT base)
         case NPY_FR_Y:
             len += 21; /* 64-bit year */
             break;
+        case NPY_DATETIMEUNIT_NULL:
+            return 0;
     }
 
     if (base >= NPY_FR_h) {
diff --git a/numpy/core/src/multiarray/item_selection.c b/numpy/core/src/multiarray/item_selection.c
index 486eb43ce..4e3181fc0 100644
--- a/numpy/core/src/multiarray/item_selection.c
+++ b/numpy/core/src/multiarray/item_selection.c
@@ -1113,7 +1113,7 @@ PyArray_Sort(PyArrayObject *op, int axis, NPY_SORTKIND which)
         return -1;
     }
 
-    if (which < 0 || which >= NPY_NSORTS) {
+    if (which >= NPY_NSORTS) {
         PyErr_SetString(PyExc_ValueError, "not a valid sort kind");
         return -1;
     }
@@ -1221,10 +1221,6 @@ PyArray_Partition(PyArrayObject *op, PyArrayObject * ktharray, int axis,
         return -1;
     }
 
-    if (which < 0 || which >= NPY_NSELECTS) {
-        PyErr_SetString(PyExc_ValueError, "not a valid partition kind");
-        return -1;
-    }
     part = get_partition_func(PyArray_TYPE(op), which);
     if (part == NULL) {
         /* Use sorting, slower but equivalent */
@@ -1263,7 +1259,7 @@ PyArray_ArgSort(PyArrayObject *op, int axis, NPY_SORTKIND which)
     PyArray_ArgSortFunc *argsort;
     PyObject *ret;
 
-    if (which < 0 || which >= NPY_NSORTS) {
+    if (which >= NPY_NSORTS) {
         PyErr_SetString(PyExc_ValueError,
                         "not a valid sort kind");
         return NULL;
@@ -1316,12 +1312,6 @@ PyArray_ArgPartition(PyArrayObject *op, PyArrayObject *ktharray, int axis,
     PyArray_ArgSortFunc *argsort;
     PyObject *ret;
 
-    if (which < 0 || which >= NPY_NSELECTS) {
-        PyErr_SetString(PyExc_ValueError,
-                        "not a valid partition kind");
-        return NULL;
-    }
-
     argpart = get_argpartition_func(PyArray_TYPE(op), which);
     if (argpart == NULL) {
         /* Use sorting, slower but equivalent */
diff --git a/numpy/core/src/private/npy_binsearch.h.src b/numpy/core/src/private/npy_binsearch.h.src
index 3b2c59487..7d7099d24 100644
--- a/numpy/core/src/private/npy_binsearch.h.src
+++ b/numpy/core/src/private/npy_binsearch.h.src
@@ -106,10 +106,6 @@ get_@arg@binsearch_func(PyArray_Descr *dtype, NPY_SEARCHSIDE side)
     npy_intp max_idx = num_funcs;
     int type = dtype->type_num;
 
-    if (side >= NPY_NSEARCHSIDES) {
-        return NULL;
-    }
-
     /*
      * It seems only fair that a binary search function be searched for
      * using a binary search...
diff --git a/numpy/core/src/private/npy_partition.h.src b/numpy/core/src/private/npy_partition.h.src
index 07aecd4f8..8345546cc 100644
--- a/numpy/core/src/private/npy_partition.h.src
+++ b/numpy/core/src/private/npy_partition.h.src
@@ -92,9 +92,6 @@ static NPY_INLINE PyArray_PartitionFunc *
 get_partition_func(int type, NPY_SELECTKIND which)
 {
     npy_intp i;
-    if (which >= NPY_NSELECTS) {
-        return NULL;
-    }
     for (i = 0; i < sizeof(_part_map)/sizeof(_part_map[0]); i++) {
         if (type == _part_map[i].typenum) {
             return _part_map[i].part[which];
@@ -108,9 +105,6 @@ static NPY_INLINE PyArray_ArgPartitionFunc *
 get_argpartition_func(int type, NPY_SELECTKIND which)
 {
     npy_intp i;
-    if (which >= NPY_NSELECTS) {
-        return NULL;
-    }
     for (i = 0; i < sizeof(_part_map)/sizeof(_part_map[0]); i++) {
         if (type == _part_map[i].typenum) {
             return _part_map[i].argpart[which];