diff --git a/parser.c b/parser.c
index 7e93175..f7ab041 100644
--- a/parser.c
+++ b/parser.c
@@ -50,7 +50,7 @@ enum token_id {
 struct token {
 	enum token_id id;
 	char *str;
-	unsigned num;
+	unsigned long long num;
 	struct qmi_struct *qmi_struct;
 };
 
@@ -169,6 +169,7 @@ static struct token yylex()
 {
 	struct symbol *sym;
 	struct token token = {};
+	unsigned long long num;
 	char buf[128];
 	char *p = buf;
 	int base;
@@ -227,8 +228,14 @@ static struct token yylex()
 		else
 			base = 10;
 
+		errno = 0;
+		num = strtoull(buf, NULL, base);
+		if (errno)
+			yyerror("number %s out of range", buf);
+
+		token.num = num;
 		token.id = TOK_NUM;
-		token.num = strtol(buf, NULL, base);
+
 		return token;
 	} else if (!ch) {
 		token.id = TOK_EOF;
diff --git a/qmic.c b/qmic.c
index f542f82..05c86c4 100644
--- a/qmic.c
+++ b/qmic.c
@@ -28,7 +28,7 @@ void qmi_const_header(FILE *fp)
 		return;
 
 	list_for_each_entry(qc, &qmi_consts, node)
-		fprintf(fp, "#define %s %d\n", qc->name, qc->value);
+		fprintf(fp, "#define %s %llu\n", qc->name, qc->value);
 
 	fprintf(fp, "\n");
 }
diff --git a/qmic.h b/qmic.h
index 670adeb..b898d04 100644
--- a/qmic.h
+++ b/qmic.h
@@ -28,7 +28,7 @@ extern const char *qmi_package;
 
 struct qmi_const {
 	const char *name;
-	unsigned value;
+	unsigned long long value;
 
 	struct list_head node;
 };
diff --git a/tests/num_large.qmi b/tests/num_large.qmi
new file mode 100644
index 0000000..96ef038
--- /dev/null
+++ b/tests/num_large.qmi
@@ -0,0 +1,23 @@
+package test;
+
+# As a 32 bit signed number, this would be negative
+const TEST_NUMBER = 0x87654321;
+# This value requires more than 32 bits to represent
+const TEST_NUMBER = 0x123456789;
+
+struct qmi_result {
+	u16 result;
+	u16 error;
+};
+
+request test_request {
+	required u8 test_number = 0x12;
+} = 0x80000000;
+
+response test_response {
+	required qmi_result r = 2;
+} = 020000000000;
+
+indication test_indication {
+	optional u64 value = 0x99;
+} = 0x7;
diff --git a/tests/num_too_big.qmi b/tests/num_too_big.qmi
new file mode 100644
index 0000000..10fe70a
--- /dev/null
+++ b/tests/num_too_big.qmi
@@ -0,0 +1,22 @@
+package test;
+
+# This value requires more than 32 bits to represent
+const TEST_NUMBER = 0x123456789;
+
+struct qmi_result {
+	u16 result;
+	u16 error;
+};
+
+request test_request {
+	required u8 test_number = 0x12;
+} = 0x100000000;
+
+response test_response {
+	required qmi_result r = 2;
+} = 040000000000;
+
+indication test_indication {
+	# This value requires more than 64 bits to represent
+	optional u64 value = 0x12345678987654321;
+} = 0x7;