diff --git a/parser.c b/parser.c
index bc3454e..b9c2efd 100644
--- a/parser.c
+++ b/parser.c
@@ -329,6 +329,7 @@ static void qmi_package_parse(void)
 
 static void qmi_const_parse()
 {
+	struct qmi_const *qcm;
 	struct qmi_const *qc;
 	struct token num_tok;
 	struct token id_tok;
@@ -338,6 +339,10 @@ static void qmi_const_parse()
 	token_expect(TOK_NUM, &num_tok);
 	token_expect(';', NULL);
 
+	list_for_each_entry(qcm, &qmi_consts, node)
+		if (!strcmp(qcm->name, id_tok.str))
+			yyerror("duplicate constant \"%s\"", qcm->name);
+
 	qc = memalloc(sizeof(struct qmi_const));
 	qc->name = id_tok.str;
 	qc->value = num_tok.num;
@@ -395,6 +400,15 @@ static void qmi_message_parse(enum message_type message_type)
 		token_expect(TOK_NUM, &num_tok);
 		token_expect(';', NULL);
 
+		list_for_each_entry(qmm, &qm->members, node) {
+			if (!strcmp(qmm->name, id_tok.str))
+				yyerror("duplicate message member \"%s\"",
+					qmm->name);
+			if (qmm->id == type_tok.num)
+				yyerror("duplicate message member number %u",
+					qmm->id);
+		}
+
 		qmm = memalloc(sizeof(struct qmi_message_member));
 		qmm->name = id_tok.str;
 		qmm->type = type_tok.num;
@@ -439,6 +453,11 @@ static void qmi_struct_parse(void)
 		token_expect(TOK_ID, &id_tok);
 		token_expect(';', NULL);
 
+		list_for_each_entry(qsm, &qs->members, node)
+			if (!strcmp(qsm->name, id_tok.str))
+				yyerror("duplicate struct member \"%s\"",
+					qsm->name);
+
 		qsm = memalloc(sizeof(struct qmi_struct_member));
 		qsm->name = id_tok.str;
 		qsm->type = type_tok.num;
diff --git a/tests/duplicate_const.qmi b/tests/duplicate_const.qmi
new file mode 100644
index 0000000..9c087e0
--- /dev/null
+++ b/tests/duplicate_const.qmi
@@ -0,0 +1,21 @@
+package test;
+
+const TEST_REQUEST_RESPONSE = 35;
+const TEST_REQUEST_RESPONSE = 35;
+
+struct qmi_result {
+	u16 result;
+	u16 error;
+};
+
+request test_request {
+	required u8 test_number = 0x12;
+} = 0x23;
+
+response test_response {
+	required qmi_result r = 2;
+} = 043;
+
+indication test_indication {
+	optional u64 value = 0x99;
+} = 0x7;
diff --git a/tests/duplicate_message_name.qmi b/tests/duplicate_message_name.qmi
new file mode 100644
index 0000000..7b9627c
--- /dev/null
+++ b/tests/duplicate_message_name.qmi
@@ -0,0 +1,21 @@
+package test;
+
+const TEST_REQUEST_RESPONSE = 35;
+
+struct qmi_result {
+	u16 result;
+	u16 error;
+};
+
+request test_request {
+	required u8 test_number = 0x12;
+	required u16 test_number = 0x11;
+} = 0x23;
+
+response test_response {
+	required qmi_result r = 2;
+} = 043;
+
+indication test_indication {
+	optional u64 value = 0x99;
+} = 0x7;
diff --git a/tests/duplicate_message_val.qmi b/tests/duplicate_message_val.qmi
new file mode 100644
index 0000000..7f84e53
--- /dev/null
+++ b/tests/duplicate_message_val.qmi
@@ -0,0 +1,22 @@
+package test;
+
+const TEST_REQUEST_RESPONSE = 35;
+const TEST_INDICATION = 07;
+
+struct qmi_result {
+	u16 result;
+	u16 error;
+};
+
+request test_request {
+	required u8 test_number = 0x1;
+	optional u16 test_number2 = 0x1;
+} = 0x23;
+
+response test_response {
+	required qmi_result r = 2;
+} = 043;
+
+indication test_indication {
+	optional u64 value = 0x99;
+} = 0x7;
diff --git a/tests/duplicate_struct_name.qmi b/tests/duplicate_struct_name.qmi
new file mode 100644
index 0000000..96f741a
--- /dev/null
+++ b/tests/duplicate_struct_name.qmi
@@ -0,0 +1,30 @@
+package test;
+
+const TEST_REQUEST_RESPONSE = 35;
+const TEST_INDICATION = 07;
+
+struct qmi_result {
+	u16 result;
+	u16 error;
+};
+
+struct test_struct {
+	u8 test_u8;
+	u8 test_u8;
+	u16 test_u16;
+	u32 test_u32;
+	u64 test_u64;
+};
+
+request test_request {
+	optional test_struct foo = 0x1;
+	required u8 test_number = 0x12;
+} = 0x23;
+
+response test_response {
+	required qmi_result r = 2;
+} = 043;
+
+indication test_indication {
+	optional u64 value = 0x99;
+} = 0x7;