diff --git a/code/ndarray.c b/code/ndarray.c
index 36c523a8..bd622718 100644
--- a/code/ndarray.c
+++ b/code/ndarray.c
@@ -42,6 +42,70 @@ STATIC mp_obj_array_t *array_new(char typecode, size_t n) {
     return o;
 }
 
+#ifdef OPENMV
+void mp_obj_slice_indices(mp_obj_t self_in, mp_int_t length, mp_bound_slice_t *result) {
+    mp_obj_slice_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_int_t start, stop, step;
+
+    if (self->step == mp_const_none) {
+        step = 1;
+    } else {
+        step = mp_obj_get_int(self->step);
+        if (step == 0) {
+            mp_raise_ValueError(translate("slice step can't be zero"));
+        }
+    }
+
+    if (step > 0) {
+        // Positive step
+        if (self->start == mp_const_none) {
+            start = 0;
+        } else {
+            start = mp_obj_get_int(self->start);
+            if (start < 0) {
+                start += length;
+            }
+            start = MIN(length, MAX(start, 0));
+        }
+
+        if (self->stop == mp_const_none) {
+            stop = length;
+        } else {
+            stop = mp_obj_get_int(self->stop);
+            if (stop < 0) {
+                stop += length;
+            }
+            stop = MIN(length, MAX(stop, 0));
+        }
+    } else {
+        // Negative step
+        if (self->start == mp_const_none) {
+            start = length - 1;
+        } else {
+            start = mp_obj_get_int(self->start);
+            if (start < 0) {
+                start += length;
+            }
+            start = MIN(length - 1, MAX(start, -1));
+        }
+
+        if (self->stop == mp_const_none) {
+            stop = -1;
+        } else {
+            stop = mp_obj_get_int(self->stop);
+            if (stop < 0) {
+                stop += length;
+            }
+            stop = MIN(length - 1, MAX(stop, -1));
+        }
+    }
+
+    result->start = start;
+    result->stop = stop;
+    result->step = step;
+}
+#endif
+
 mp_float_t ndarray_get_float_value(void *data, uint8_t typecode, size_t index) {
     if(typecode == NDARRAY_UINT8) {
         return (mp_float_t)((uint8_t *)data)[index];
diff --git a/code/ndarray.h b/code/ndarray.h
index 285db971..bd0c9325 100644
--- a/code/ndarray.h
+++ b/code/ndarray.h
@@ -26,12 +26,26 @@
 #define FLOAT_TYPECODE 'd'
 #endif
 
+#ifdef OPENMV
+#define mp_obj_is_bool(o) (MP_OBJ_IS_TYPE((o), &mp_type_bool))
+#define translate(x) x
+
+typedef struct _mp_obj_slice_t {
+    mp_obj_base_t base;
+    mp_obj_t start;
+    mp_obj_t stop;
+    mp_obj_t step;
+} mp_obj_slice_t;
+
+void mp_obj_slice_get(mp_obj_t self_in, mp_obj_t *, mp_obj_t *, mp_obj_t *);
+#else
 #if CIRCUITPY
 #define mp_obj_is_bool(o) (MP_OBJ_IS_TYPE((o), &mp_type_bool))
 #define mp_obj_is_int(x) (MP_OBJ_IS_INT((x)))
 #else
 #define translate(x) MP_ERROR_TEXT(x)
 #endif
+#endif
 
 #define SWAP(t, a, b) { t tmp = a; a = b; b = tmp; }
 
diff --git a/code/ulab.c b/code/ulab.c
index 49260c53..504e8dbf 100644
--- a/code/ulab.c
+++ b/code/ulab.c
@@ -32,7 +32,7 @@
 #include "approx.h"
 #include "extras.h"
 
-STATIC MP_DEFINE_STR_OBJ(ulab_version_obj, "0.50.1");
+STATIC MP_DEFINE_STR_OBJ(ulab_version_obj, "0.50.2");
 
 MP_DEFINE_CONST_FUN_OBJ_KW(ndarray_flatten_obj, 1, ndarray_flatten);
 
@@ -116,7 +116,11 @@ STATIC MP_DEFINE_CONST_DICT (
     ulab_globals_table
 );
 
-mp_obj_module_t ulab_user_cmodule = {
+#ifdef OPENMV
+const struct _mp_obj_module_t ulab_user_cmodule = {
+#else
+const mp_obj_module_t ulab_user_cmodule = {
+#endif
     .base = { &mp_type_module },
     .globals = (mp_obj_dict_t*)&mp_module_ulab_globals,
 };
diff --git a/docs/ulab-change-log.md b/docs/ulab-change-log.md
index ed4cc06c..4bb3392f 100644
--- a/docs/ulab-change-log.md
+++ b/docs/ulab-change-log.md
@@ -1,3 +1,9 @@
+Fri, 12 Jun 2020
+
+version 0.50.2
+
+    fixes compilation error in openmv
+
 Mon, 1 Jun 2020
 
 version 0.50.1