diff --git a/src/c/array.d b/src/c/array.d
index 93ea441ce..66c138a56 100644
--- a/src/c/array.d
+++ b/src/c/array.d
@@ -671,6 +671,15 @@ ecl_elttype_to_symbol(cl_elttype aet)
         return ecl_aet_name[aet];
 }
 
+cl_object
+si_array_element_type_byte_size(cl_object type) {
+	cl_elttype aet = ecl_symbol_to_elttype(type);
+	cl_object size = MAKE_FIXNUM(ecl_aet_size[aet]);
+	if (aet == aet_bit)
+		size = ecl_make_ratio(MAKE_FIXNUM(1),MAKE_FIXNUM(CHAR_BIT));
+	@(return size ecl_elttype_to_symbol(aet))
+}
+
 static void *
 address_inc(void *address, cl_fixnum inc, cl_elttype elt_type)
 {
diff --git a/src/c/symbols_list.h b/src/c/symbols_list.h
index 65cce3c62..102f85def 100755
--- a/src/c/symbols_list.h
+++ b/src/c/symbols_list.h
@@ -1928,6 +1928,8 @@ cl_symbols[] = {
 {SYS_ "SERIALIZE", SI_ORDINARY, si_serialize, 1, OBJNULL},
 {SYS_ "DESERIALIZE", SI_ORDINARY, si_deserialize, 1, OBJNULL},
 
+{EXT_ "ARRAY-ELEMENT-TYPE-BYTE-SIZE", EXT_ORDINARY, si_array_element_type_byte_size, 1, OBJNULL},
+
 #ifdef ECL_SSE2
 {EXT_ "SSE-PACK", EXT_ORDINARY, NULL, -1, OBJNULL},
 {EXT_ "SSE-PACK-P", EXT_ORDINARY, si_sse_pack_p, 1, OBJNULL},
diff --git a/src/c/symbols_list2.h b/src/c/symbols_list2.h
index 14a7fefbd..8e5d9fe7f 100755
--- a/src/c/symbols_list2.h
+++ b/src/c/symbols_list2.h
@@ -1928,6 +1928,8 @@ cl_symbols[] = {
 {SYS_ "SERIALIZE","si_serialize"},
 {SYS_ "DESERIALIZE","si_deserialize"},
 
+{EXT_ "ARRAY-ELEMENT-TYPE-BYTE-SIZE","si_array_element_type_byte_size"},
+
 #ifdef ECL_SSE2
 {EXT_ "SSE-PACK",NULL},
 {EXT_ "SSE-PACK-P","si_sse_pack_p"},
diff --git a/src/h/external.h b/src/h/external.h
index 4fafefed2..ba45b6165 100755
--- a/src/h/external.h
+++ b/src/h/external.h
@@ -335,6 +335,7 @@ extern ECL_API cl_object cl_array_total_size(cl_object a);
 extern ECL_API cl_object cl_adjustable_array_p(cl_object a);
 extern ECL_API cl_object cl_array_displacement(cl_object a);
 extern ECL_API cl_object si_array_raw_data(cl_object array);
+extern ECL_API cl_object si_array_element_type_byte_size(cl_object type);
 extern ECL_API cl_object cl_svref(cl_object x, cl_object index);
 extern ECL_API cl_object si_svset(cl_object x, cl_object index, cl_object v);
 extern ECL_API cl_object cl_array_has_fill_pointer_p(cl_object a);