diff --git a/lib/am.c b/lib/am.c
index cf32605..6c98bd3 100644
--- a/lib/am.c
+++ b/lib/am.c
@@ -26,13 +26,13 @@ void am_pop(am_t *am, am_reg_t reg)
 	am->regs[reg] = *++am->sp;
 }
 
-void am_append_arg(am_t *am)
+void am_append(am_t *am, am_reg_t list_reg, am_reg_t item_reg)
 {
-	expr_t *list = AM_ARGL(am);
+	expr_t *list = am->regs[list_reg];
 	while (!list->is_atom)
 		list = list->pair.cdr;
 
 	list->is_atom = false;
-	list->pair.car = AM_VAL(am);
+	list->pair.car = am->regs[item_reg];
 	list->pair.cdr = expr_empty_list(am);
 }
diff --git a/lib/eval.c b/lib/eval.c
index 386a4a2..6e47e2e 100644
--- a/lib/eval.c
+++ b/lib/eval.c
@@ -34,7 +34,7 @@ static void eval_list(am_t *am)
 		eval(am);
 
 		am_pop(am, ARGL);
-		am_append_arg(am);
+		am_append(am, ARGL, VAL);
 
 		am_pop(am, UNEV);
 		am_pop(am, EXPR);
diff --git a/lib/include/am.h b/lib/include/am.h
index 36240f0..4f3072d 100644
--- a/lib/include/am.h
+++ b/lib/include/am.h
@@ -31,6 +31,6 @@ typedef struct am {
 void am_init(am_t *am);
 void am_push(am_t *am, am_reg_t reg);
 void am_pop(am_t *am, am_reg_t reg);
-void am_append_arg(am_t *am);
+void am_append(am_t *am, am_reg_t list_reg, am_reg_t item_reg);
 
 #endif
diff --git a/lib/parse.c b/lib/parse.c
index 7622485..8194c0c 100644
--- a/lib/parse.c
+++ b/lib/parse.c
@@ -22,18 +22,6 @@ static parse_state_t pop_state(parse_ctx_t *ctx)
 	return *++ctx->sp;
 }
 
-static void append(parse_ctx_t *ctx, expr_t *expr)
-{
-	expr_t *list = AM_EXPR(ctx->am);
-	while (!list->is_atom)
-		list = list->pair.cdr;
-	assert(list->atom.type == ATOM_TYPE_EMPTY_LIST);
-
-	list->is_atom = false;
-	list->pair.car = expr;
-	list->pair.cdr = expr_empty_list(ctx->am);
-}
-
 parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token)
 {
 	switch (ctx->state) {
@@ -61,10 +49,12 @@ parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token)
 	case PARSE_STATE_LIST:
 		switch (token->type) {
 		case TOKEN_TYPE_INTEGER:
-			append(ctx, expr_integer(ctx->am, token->integer));
+			AM_VAL(ctx->am) = expr_integer(ctx->am, token->integer);
+			am_append(ctx->am, EXPR, VAL);
 			break;
 		case TOKEN_TYPE_SYMBOL:
-			append(ctx, expr_symbol(ctx->am, &token->symbol));
+			AM_VAL(ctx->am) = expr_symbol(ctx->am, &token->symbol);
+			am_append(ctx->am, EXPR, VAL);
 			break;
 		case TOKEN_TYPE_OPEN_PAREN:
 			am_push(ctx->am, EXPR);
@@ -75,9 +65,9 @@ parse_state_t parse_proc(parse_ctx_t *ctx, const token_t *token)
 		case TOKEN_TYPE_CLOSE_PAREN:
 			ctx->state = pop_state(ctx);
 			if (ctx->state == PARSE_STATE_LIST) {
-				expr_t *expr = AM_EXPR(ctx->am);
+				AM_VAL(ctx->am) = AM_EXPR(ctx->am);
 				am_pop(ctx->am, EXPR);
-				append(ctx, expr);
+				am_append(ctx->am, EXPR, VAL);
 			}
 			break;
 		}
diff --git a/tests/am_tests.c b/tests/am_tests.c
index 06ac962..d3e46df 100644
--- a/tests/am_tests.c
+++ b/tests/am_tests.c
@@ -3,6 +3,7 @@
 
 #define CAR(expr) (expr->pair.car)
 #define CDR(expr) (expr->pair.cdr)
+#define CADR(expr) CAR(CDR(expr))
 
 static am_t am;
 
@@ -39,11 +40,11 @@ static void test_argl_value_restored_after_push_modify_pop(void)
 	TEST_ASSERT_EQUAL(&a, am.regs[ARGL]);
 }
 
-static void test_append_arg_42_with_empty_argl(void)
+static void test_append_val_42_to_empty_argl(void)
 {
 	am.regs[ARGL] = expr_empty_list(&am);
 	am.regs[VAL] = expr_integer(&am, 42);
-	am_append_arg(&am);
+	am_append(&am, ARGL, VAL);
 
 	TEST_ASSERT_FALSE(am.regs[ARGL]->is_atom);
 	TEST_ASSERT_NOT_NULL(CAR(am.regs[ARGL]));
@@ -56,11 +57,36 @@ static void test_append_arg_42_with_empty_argl(void)
 	TEST_ASSERT_EQUAL(ATOM_TYPE_EMPTY_LIST, CDR(am.regs[ARGL])->atom.type);
 }
 
+static void test_append_unev_2_to_expr_list_1(void)
+{
+	am.regs[EXPR]
+	    = expr_pair(&am, expr_integer(&am, 1), expr_empty_list(&am));
+	am.regs[UNEV] = expr_integer(&am, 2);
+	am_append(&am, EXPR, UNEV);
+
+	TEST_ASSERT_NOT_NULL(am.regs[EXPR]);
+	TEST_ASSERT_FALSE(am.regs[EXPR]->is_atom);
+
+	TEST_ASSERT_NOT_NULL(CAR(am.regs[EXPR]));
+	TEST_ASSERT_TRUE(CAR(am.regs[EXPR])->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, CAR(am.regs[EXPR])->atom.type);
+	TEST_ASSERT_EQUAL(1, CAR(am.regs[EXPR])->atom.integer);
+
+	TEST_ASSERT_NOT_NULL(CDR(am.regs[EXPR]));
+	TEST_ASSERT_FALSE(CDR(am.regs[EXPR])->is_atom);
+
+	TEST_ASSERT_NOT_NULL(CADR(am.regs[EXPR]));
+	TEST_ASSERT_TRUE(CADR(am.regs[EXPR])->is_atom);
+	TEST_ASSERT_EQUAL(ATOM_TYPE_INTEGER, CADR(am.regs[EXPR])->atom.type);
+	TEST_ASSERT_EQUAL(2, CADR(am.regs[EXPR])->atom.integer);
+}
+
 int main(void)
 {
 	UNITY_BEGIN();
 	RUN_TEST(test_expr_value_restored_after_push_modify_pop);
 	RUN_TEST(test_argl_value_restored_after_push_modify_pop);
-	RUN_TEST(test_append_arg_42_with_empty_argl);
+	RUN_TEST(test_append_val_42_to_empty_argl);
+	RUN_TEST(test_append_unev_2_to_expr_list_1);
 	return UNITY_END();
 }