diff --git a/vlib/v/checker/assign.v b/vlib/v/checker/assign.v
index 1987f34859..56e9993478 100644
--- a/vlib/v/checker/assign.v
+++ b/vlib/v/checker/assign.v
@@ -361,7 +361,7 @@ pub fn (mut c Checker) assign_stmt(mut node ast.AssignStmt) {
 					node.pos)
 			}
 		}
-		if left_sym.kind == .array && right_sym.kind == .array {
+		if left_sym.kind == .array && right_sym.kind == .array && node.op == .assign {
 			// `mut arr := [u8(1),2,3]`
 			// `arr = [byte(4),5,6]`
 			left_info := left_sym.info as ast.Array
diff --git a/vlib/v/checker/tests/array_plus_assign_err.out b/vlib/v/checker/tests/array_plus_assign_err.out
new file mode 100644
index 0000000000..fb1ed8b4c9
--- /dev/null
+++ b/vlib/v/checker/tests/array_plus_assign_err.out
@@ -0,0 +1,8 @@
+vlib/v/checker/tests/array_plus_assign_err.vv:1:5: warning: unused variable: `buffer`
+    1 | mut buffer := []u8{cap: 1024}
+      |     ~~~~~~
+    2 | buffer += "ipconfig && sudo apt-get install -y some_amazing_package name + command output".bytes()
+vlib/v/checker/tests/array_plus_assign_err.vv:2:1: error: operator `+=` not defined on left operand type `[]u8`
+    1 | mut buffer := []u8{cap: 1024}
+    2 | buffer += "ipconfig && sudo apt-get install -y some_amazing_package name + command output".bytes()
+      | ~~~~~~
\ No newline at end of file
diff --git a/vlib/v/checker/tests/array_plus_assign_err.vv b/vlib/v/checker/tests/array_plus_assign_err.vv
new file mode 100644
index 0000000000..12c5505fdd
--- /dev/null
+++ b/vlib/v/checker/tests/array_plus_assign_err.vv
@@ -0,0 +1,2 @@
+mut buffer := []u8{cap: 1024}
+buffer += "ipconfig && sudo apt-get install -y some_amazing_package name + command output".bytes()
\ No newline at end of file