diff --git a/src/brei-shared.c b/src/brei-shared.c
index 6522069..edf07bb 100644
--- a/src/brei-shared.c
+++ b/src/brei-shared.c
@@ -532,8 +532,10 @@ MUNIT_TEST(test_brei_send_message)
 	int sock_read = sv[0];
 	int sock_write = sv[1];
 
+	const int header_size = 8;
+
 	{
-		const int msglen = 16; /* 8 header + 2 * 4 bytes */
+		const int msglen = header_size + 8; /* 2 * 4 bytes */
 		object_id_t id = 1;
 		uint32_t opcode = 2;
 		const char *signature = "uu";
@@ -549,7 +551,7 @@ MUNIT_TEST(test_brei_send_message)
 		munit_assert_int(buf[3], ==, 0xdddd);
 	}
 	{
-		const int msglen = 16; /* 8 header + 2 * 4 bytes */
+		const int msglen = header_size + 8; /* 2 * 4 bytes */
 		object_id_t id = 1;
 		uint32_t opcode = 2;
 		const char *signature = "fi";
@@ -575,7 +577,7 @@ MUNIT_TEST(test_brei_send_message)
 		int slen = bytes_to_int32(strlen(string) + 1) * 4;
 		munit_assert_int(slen, ==, sizeof(string));
 
-		const int msglen = 24 + slen; /* 8 header + 3 * 4 bytes + 4 bytes slen + string length */
+		const int msglen = header_size + 16 + slen; /* 3 * 4 bytes + 4 bytes slen + string length */
 		object_id_t id = 2;
 		uint32_t opcode = 3;
 		const char *signature = "ison";
@@ -601,7 +603,7 @@ MUNIT_TEST(test_brei_send_message)
 		const char string1[12] = "hello wor"; /* tests padding too */
 		const char string2[8] = "barba"; /* tests padding too */
 
-		const int msglen = 16 + sizeof(string1) + sizeof(string2); /* 8 header + 2 * 4 bytes slen + string lengths */
+		const int msglen = header_size + 8 + sizeof(string1) + sizeof(string2); /* 8 header + 2 * 4 bytes slen + string lengths */
 		object_id_t id = 2;
 		uint32_t opcode = 3;
 		const char *signature = "ss";
@@ -629,7 +631,7 @@ MUNIT_TEST(test_brei_send_message)
 		/* actual message data to be sent */
 		char data[] = "some data\n";
 
-		const int msglen = 16; /* 8 header, 2 unsigned, fd is not in data */
+		const int msglen = header_size + 8; /* 2 unsigned, fd is not in data */
 		object_id_t id = 2;
 		uint32_t opcode = 3;
 		const char *signature = "uhu";