diff --git a/Makefile b/Makefile
index 94dd0ec..a5b37b5 100644
--- a/Makefile
+++ b/Makefile
@@ -40,7 +40,7 @@ tags:
 	ctags *.[ch] **/*.[ch]
 
 clean:
-	rm -f nextlang *.o builtins/*.o
+	rm -f nextlang *.o builtins/*.o libnext.so
 
 %.1: %.1.md
 	pandoc --lua-filter=.pandoc/bold-code.lua -s $< -t man -o $@
diff --git a/builtins/array.c b/builtins/array.c
index 4f9070f..85eaeb8 100644
--- a/builtins/array.c
+++ b/builtins/array.c
@@ -228,30 +228,30 @@ public array_t Array__slice(array_t *array, int64_t first, int64_t stride, int64
     };
 }
 
-array_t Array__concat(array_t *x, array_t *y, const TypeInfo *type)
+public array_t Array__concat(array_t x, array_t y, const TypeInfo *type)
 {
     int64_t item_size = get_item_size(type);
-    void *data = x->atomic ? GC_MALLOC_ATOMIC(item_size*(x->length + y->length)) : GC_MALLOC(item_size*(x->length + y->length));
-    if (x->stride == item_size) {
-        memcpy(data, x->data, item_size*x->length);
+    void *data = x.atomic ? GC_MALLOC_ATOMIC(item_size*(x.length + y.length)) : GC_MALLOC(item_size*(x.length + y.length));
+    if (x.stride == item_size) {
+        memcpy(data, x.data, item_size*x.length);
     } else {
-        for (int64_t i = 0; i < x->length; i++)
-            memcpy(data + i*item_size, x->data + i*item_size, item_size);
+        for (int64_t i = 0; i < x.length; i++)
+            memcpy(data + i*item_size, x.data + i*item_size, item_size);
     }
 
-    if (y->stride == item_size) {
-        memcpy(data + item_size*x->length, y->data, item_size*y->length);
+    if (y.stride == item_size) {
+        memcpy(data + item_size*x.length, y.data, item_size*y.length);
     } else {
-        for (int64_t i = 0; i < x->length; i++)
-            memcpy(data + (x->length + i)*item_size, y->data + i*item_size, item_size);
+        for (int64_t i = 0; i < x.length; i++)
+            memcpy(data + (x.length + i)*item_size, y.data + i*item_size, item_size);
     }
 
     return (array_t){
         .data=data,
-        .length=x->length + y->length,
+        .length=x.length + y.length,
         .stride=item_size,
         .copy_on_write=0,
-        .atomic=x->atomic,
+        .atomic=x.atomic,
     };
 }
 
diff --git a/builtins/array.h b/builtins/array.h
index 5a4b29a..0cbc12f 100644
--- a/builtins/array.h
+++ b/builtins/array.h
@@ -32,7 +32,7 @@ void Array__clear(array_t *array, const TypeInfo *type);
 void Array__compact(array_t *arr, const TypeInfo *type);
 bool Array__contains(array_t array, void *item, const TypeInfo *type);
 array_t Array__slice(array_t *array, int64_t first, int64_t stride, int64_t length, bool readonly, const TypeInfo *type);
-array_t Array__concat(array_t *x, array_t *y, const TypeInfo *type);
+array_t Array__concat(array_t x, array_t y, const TypeInfo *type);
 uint32_t Array__hash(const array_t *arr, const TypeInfo *type);
 int32_t Array__compare(const array_t *x, const array_t *y, const TypeInfo *type);
 bool Array__equal(const array_t *x, const array_t *y, const TypeInfo *type);
diff --git a/compile.c b/compile.c
index 0690880..56e8b5a 100644
--- a/compile.c
+++ b/compile.c
@@ -374,12 +374,16 @@ CORD compile(env_t *env, ast_t *ast)
         }
         case BINOP_XOR: return CORD_asprintf("%r ^= %r;", lhs, rhs);
         case BINOP_CONCAT: {
-            if (operand_t->tag == StringType)
+            if (operand_t->tag == StringType) {
                 return CORD_asprintf("%r = CORD_cat(%r, %r);", lhs, lhs, rhs);
-            else if (operand_t->tag == ArrayType)
-                return CORD_all(lhs, "Array__concat(", lhs, ", ", rhs, ", ", compile_type_info(env, operand_t), ")");
-            else
+            } else if (operand_t->tag == ArrayType) {
+                if (update->lhs->tag == Var)
+                    return CORD_all("Array__insert_all(&", lhs, ", ", rhs, ", 0, ", compile_type_info(env, operand_t), ")");
+                else
+                    return CORD_all(lhs, "Array__concat(", lhs, ", ", rhs, ", ", compile_type_info(env, operand_t), ")");
+            } else {
                 code_err(ast, "'++=' is not implemented for %T types", operand_t);
+            }
         }
         default: code_err(ast, "Update assignments are not implemented for this operation");
         }