diff --git a/compiler/parser.v b/compiler/parser.v
index 0e4ccaf0d8..64cade9538 100644
--- a/compiler/parser.v
+++ b/compiler/parser.v
@@ -2000,6 +2000,7 @@ fn (p mut Parser) index_expr(typ_ string, fn_ph int) string {
 			p.error('strings are immutable')
 		}
 		assign_pos := p.cgen.cur_line.len
+		is_cao := p.tok != .assign
 		p.assigned_type = typ
 		p.expected_type = typ
 		p.assign_statement(v, fn_ph, is_indexer && (is_map || is_arr))
@@ -2013,19 +2014,33 @@ fn (p mut Parser) index_expr(typ_ string, fn_ph int) string {
 			tmp_val := p.cgen.cur_line.right(assign_pos)
 			p.cgen.resetln(p.cgen.cur_line.left(assign_pos))
 			// val := p.cgen.end_tmp()
+			mut cao_tmp := p.cgen.cur_line
 			if is_map {
 				p.cgen.set_placeholder(fn_ph, 'map__set(&')
+				// CAO on map is a bit more complicated as it loads
+				// the value inside a pointer instead of returning it.
 			}
 			else {
 				if is_ptr {
 					p.cgen.set_placeholder(fn_ph, 'array_set(')
+					if is_cao {
+						cao_tmp = '*($p.expected_type *) array__get(*$cao_tmp)'
+					}
 				}
 				else {
 					p.cgen.set_placeholder(fn_ph, 'array_set(&/*q*/')
+					if is_cao {
+						cao_tmp = '*($p.expected_type *) array__get($cao_tmp)'
+					}
 				}
 			}
 			p.gen(', & $tmp)')
-			p.cgen.insert_before('$typ $tmp = $tmp_val;')
+			if !is_cao {
+				p.cgen.insert_before('$typ $tmp = $tmp_val;')
+			}
+			else {
+				p.cgen.insert_before('$typ $tmp = $cao_tmp ' + tmp_val.all_before('=') + tmp_val.all_after('=') + ';')
+			}
 		}
 		return typ
 	}
diff --git a/vlib/builtin/array_test.v b/vlib/builtin/array_test.v
index 888b9b04a0..516d6b653b 100644
--- a/vlib/builtin/array_test.v
+++ b/vlib/builtin/array_test.v
@@ -199,3 +199,10 @@ fn test_clone() {
 	assert nums.slice(1, 3).str() == '[2, 3]' 
 } 
  
+fn test_doubling() {
+	mut nums := [1, 2, 3, 4, 5]
+	for i := 0; i < nums.len; i++ {
+		nums[i] *= 2
+	}
+	assert nums.str() == '[2, 4, 6, 8, 10]'
+}
\ No newline at end of file