diff --git a/shapito/be_read.c b/shapito/be_read.c
index 713b6e22..0b689a66 100644
--- a/shapito/be_read.c
+++ b/shapito/be_read.c
@@ -110,7 +110,7 @@ shapito_be_read_password(shapito_password_t *pw, char *data, uint32_t size)
 	int rc = shapito_read(&len, &data, &size);
 	if (shapito_unlikely(rc != 0))
 		return -1;
-	if (shapito_unlikely(header->type != 'p'))
+	if (shapito_unlikely(header->type != SHAPITO_FE_PASSWORD_MESSAGE))
 		return -1;
 	pw->password_len = len;
 	pw->password = malloc(len);
@@ -128,7 +128,7 @@ shapito_be_read_query(char **query, uint32_t *query_len, char *data, uint32_t si
 	int rc = shapito_read(&len, &data, &size);
 	if (shapito_unlikely(rc != 0))
 		return -1;
-	if (shapito_unlikely(header->type != 'Q'))
+	if (shapito_unlikely(header->type != SHAPITO_FE_QUERY))
 		return -1;
 	*query = header->data;
 	*query_len = len;
diff --git a/shapito/be_write.h b/shapito/be_write.h
index 69d82abc..2cf35ece 100644
--- a/shapito/be_write.h
+++ b/shapito/be_write.h
@@ -24,7 +24,7 @@ shapito_be_write_error_as(shapito_stream_t *stream, char *severity, char *code,
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + size);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'E');
+	shapito_stream_write8(stream, SHAPITO_BE_ERROR_RESPONSE);
 	shapito_stream_write32(stream, sizeof(uint32_t) + size);
 	shapito_stream_write8(stream, 'S');
 	shapito_stream_write(stream, severity, 6);
@@ -71,7 +71,7 @@ shapito_be_write_notice(shapito_stream_t *stream, char *message, int len)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + len + 1);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'N');
+	shapito_stream_write8(stream, SHAPITO_BE_NOTICE_RESPONSE);
 	shapito_stream_write32(stream, sizeof(uint32_t) + len);
 	shapito_stream_write(stream, message, len);
 	shapito_stream_write8(stream, 0);
@@ -84,7 +84,7 @@ shapito_be_write_authentication_ok(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + sizeof(uint32_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'R');
+	shapito_stream_write8(stream, SHAPITO_BE_AUTHENTICATION);
 	shapito_stream_write32(stream, sizeof(uint32_t) + sizeof(uint32_t));
 	shapito_stream_write32(stream, 0);
 	return 0;
@@ -96,7 +96,7 @@ shapito_be_write_authentication_clear_text(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + sizeof(uint32_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'R');
+	shapito_stream_write8(stream, SHAPITO_BE_AUTHENTICATION);
 	shapito_stream_write32(stream, sizeof(uint32_t) + sizeof(uint32_t));
 	shapito_stream_write32(stream, 3);
 	return 0;
@@ -108,7 +108,7 @@ shapito_be_write_authentication_md5(shapito_stream_t *stream, char salt[4])
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + sizeof(uint32_t) + 4);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'R');
+	shapito_stream_write8(stream, SHAPITO_BE_AUTHENTICATION);
 	shapito_stream_write32(stream, sizeof(uint32_t) + sizeof(uint32_t) + 4);
 	shapito_stream_write32(stream, 5);
 	shapito_stream_write(stream, salt, 4);
@@ -123,7 +123,7 @@ shapito_be_write_backend_key_data(shapito_stream_t *stream, uint32_t pid, uint32
 	                               sizeof(uint32_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'K');
+	shapito_stream_write8(stream, SHAPITO_BE_BACKEND_KEY_DATA);
 	shapito_stream_write32(stream, sizeof(uint32_t) + sizeof(uint32_t) +
 	                       sizeof(uint32_t));
 	shapito_stream_write32(stream, pid);
@@ -138,7 +138,7 @@ shapito_be_write_parameter_status(shapito_stream_t *stream, char *key, int key_l
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + key_len + value_len);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'S');
+	shapito_stream_write8(stream, SHAPITO_BE_PARAMETER_STATUS);
 	shapito_stream_write32(stream, sizeof(uint32_t) + key_len + value_len);
 	shapito_stream_write(stream, key, key_len);
 	shapito_stream_write(stream, value, value_len);
@@ -151,7 +151,7 @@ shapito_be_write_ready(shapito_stream_t *stream, uint8_t status)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + sizeof(uint8_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'Z');
+	shapito_stream_write8(stream, SHAPITO_BE_READY_FOR_QUERY);
 	shapito_stream_write32(stream, sizeof(uint32_t) + sizeof(uint8_t));
 	shapito_stream_write8(stream, status);
 	return 0;
@@ -164,7 +164,7 @@ shapito_be_write_row_description(shapito_stream_t *stream)
 	if (shapito_unlikely(rc == -1))
 		return -1;
 	int position = shapito_stream_used(stream);
-	shapito_stream_write8(stream, 'T');
+	shapito_stream_write8(stream, SHAPITO_BE_ROW_DESCRIPTION);
 	shapito_stream_write32(stream, sizeof(uint32_t) + sizeof(uint16_t));
 	shapito_stream_write16(stream, 0);
 	return position;
@@ -260,7 +260,7 @@ shapito_be_write_data_row(shapito_stream_t *stream)
 	if (shapito_unlikely(rc == -1))
 		return -1;
 	int position = shapito_stream_used(stream);
-	shapito_stream_write8(stream, 'D');
+	shapito_stream_write8(stream, SHAPITO_BE_DATA_ROW);
 	shapito_stream_write32(stream, sizeof(uint32_t) + sizeof(uint16_t));
 	shapito_stream_write16(stream, 0);
 	return position;
@@ -299,7 +299,7 @@ shapito_be_write_complete(shapito_stream_t *stream, char *message, int len)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + len);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'C');
+	shapito_stream_write8(stream, SHAPITO_BE_COMMAND_COMPLETE);
 	shapito_stream_write32(stream, sizeof(uint32_t) + len);
 	shapito_stream_write(stream, message, len);
 	return 0;
@@ -311,7 +311,7 @@ shapito_be_write_empty_query(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'I');
+	shapito_stream_write8(stream, SHAPITO_BE_EMPTY_QUERY_RESPONSE);
 	shapito_stream_write32(stream, sizeof(uint32_t));
 	return 0;
 }
@@ -322,7 +322,7 @@ shapito_be_write_parse_complete(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, '1');
+	shapito_stream_write8(stream, SHAPITO_BE_PARSE_COMPLETE);
 	shapito_stream_write32(stream, sizeof(uint32_t));
 	return 0;
 }
@@ -333,7 +333,7 @@ shapito_be_write_bind_complete(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, '2');
+	shapito_stream_write8(stream, SHAPITO_BE_BIND_COMPLETE);
 	shapito_stream_write32(stream, sizeof(uint32_t));
 	return 0;
 }
@@ -344,7 +344,7 @@ shapito_be_write_portal_suspended(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 's');
+	shapito_stream_write8(stream, SHAPITO_BE_PORTAL_SUSPENDED);
 	shapito_stream_write32(stream, sizeof(uint32_t));
 	return 0;
 }
@@ -355,7 +355,7 @@ shapito_be_write_no_data(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'n');
+	shapito_stream_write8(stream, SHAPITO_BE_NO_DATA);
 	shapito_stream_write32(stream, sizeof(uint32_t));
 	return 0;
 }
diff --git a/shapito/fe_read.c b/shapito/fe_read.c
index 86dfc8ae..4847198b 100644
--- a/shapito/fe_read.c
+++ b/shapito/fe_read.c
@@ -15,7 +15,7 @@ shapito_fe_read_ready(int *status, char *data, uint32_t size)
 	int rc = shapito_read(&len, &data, &size);
 	if (shapito_unlikely(rc != 0))
 		return -1;
-	if (shapito_unlikely(header->type != 'Z' || len != 1))
+	if (shapito_unlikely(header->type != SHAPITO_BE_READY_FOR_QUERY || len != 1))
 		return -1;
 	*status = header->data[0];
 	return 0;
@@ -29,7 +29,7 @@ shapito_fe_read_key(shapito_key_t *key, char *data, uint32_t size)
 	int rc = shapito_read(&len, &data, &size);
 	if (shapito_unlikely(rc != 0))
 		return -1;
-	if (shapito_unlikely(header->type != 'K' || len != 8))
+	if (shapito_unlikely(header->type != SHAPITO_BE_BACKEND_KEY_DATA || len != 8))
 		return -1;
 	uint32_t pos_size = len;
 	char *pos = header->data;
@@ -50,7 +50,7 @@ shapito_fe_read_auth(uint32_t *type, char salt[4], char *data, uint32_t size)
 	int rc = shapito_read(&len, &data, &size);
 	if (shapito_unlikely(rc != 0))
 		return -1;
-	if (shapito_unlikely(header->type != 'R'))
+	if (shapito_unlikely(header->type != SHAPITO_BE_AUTHENTICATION))
 		return -1;
 	uint32_t pos_size = len;
 	char *pos = header->data;
@@ -85,7 +85,7 @@ shapito_fe_read_parameter(char *data, uint32_t size,
 	int rc = shapito_read(&len, &data, &size);
 	if (shapito_unlikely(rc != 0))
 		return -1;
-	if (shapito_unlikely(header->type != 'S'))
+	if (shapito_unlikely(header->type != SHAPITO_BE_PARAMETER_STATUS))
 		return -1;
 	uint32_t pos_size = len;
 	char *pos = header->data;
@@ -112,7 +112,7 @@ shapito_fe_read_error(shapito_fe_error_t *error, char *data, uint32_t size)
 	int rc = shapito_read(&len, &data, &size);
 	if (shapito_unlikely(rc != 0))
 		return -1;
-	if (shapito_unlikely(header->type != 'E'))
+	if (shapito_unlikely(header->type != SHAPITO_BE_ERROR_RESPONSE))
 		return -1;
 	memset(error, 0, sizeof(*error));
 	uint32_t pos_size = len;
diff --git a/shapito/fe_write.h b/shapito/fe_write.h
index 09e243c4..27f9a475 100644
--- a/shapito/fe_write.h
+++ b/shapito/fe_write.h
@@ -81,7 +81,7 @@ shapito_fe_write_terminate(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'X');
+	shapito_stream_write8(stream, SHAPITO_FE_TERMINATE);
 	shapito_stream_write32(stream, sizeof(uint32_t));
 	return 0;
 }
@@ -92,7 +92,7 @@ shapito_fe_write_password(shapito_stream_t *stream, char *password, int len)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + len);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'p');
+	shapito_stream_write8(stream, SHAPITO_FE_PASSWORD_MESSAGE);
 	shapito_stream_write32(stream, sizeof(uint32_t) + len);
 	shapito_stream_write(stream, password, len);
 	return 0;
@@ -104,7 +104,7 @@ shapito_fe_write_query(shapito_stream_t *stream, char *query, int len)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + len);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'Q');
+	shapito_stream_write8(stream, SHAPITO_FE_QUERY);
 	shapito_stream_write32(stream, sizeof(uint32_t) + len);
 	shapito_stream_write(stream, query, len);
 	return 0;
@@ -121,7 +121,7 @@ shapito_fe_write_parse(shapito_stream_t *stream,
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + size);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'P');
+	shapito_stream_write8(stream, SHAPITO_FE_PARSE);
 	shapito_stream_write32(stream, sizeof(uint32_t) + size);
 	shapito_stream_write(stream, operator_name, operator_len);
 	shapito_stream_write(stream, query, query_len);
@@ -156,7 +156,7 @@ shapito_fe_write_bind(shapito_stream_t *stream,
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + size);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'B');
+	shapito_stream_write8(stream, SHAPITO_FE_BIND);
 	shapito_stream_write32(stream, sizeof(uint32_t) + size);
 	shapito_stream_write(stream, portal_name, portal_len);
 	shapito_stream_write(stream, operator_name, operator_len);
@@ -186,7 +186,7 @@ shapito_fe_write_describe(shapito_stream_t *stream, uint8_t type, char *name, in
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + size);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'D');
+	shapito_stream_write8(stream, SHAPITO_FE_DESCRIBE);
 	shapito_stream_write32(stream, sizeof(uint32_t) + size);
 	shapito_stream_write8(stream, type);
 	shapito_stream_write(stream, name, name_len);
@@ -200,7 +200,7 @@ shapito_fe_write_execute(shapito_stream_t *stream, char *portal, int portal_len,
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t) + size);
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'E');
+	shapito_stream_write8(stream, SHAPITO_FE_EXECUTE);
 	shapito_stream_write32(stream, sizeof(uint32_t) + size);
 	shapito_stream_write(stream, portal, portal_len);
 	shapito_stream_write32(stream, limit);
@@ -213,7 +213,7 @@ shapito_fe_write_sync(shapito_stream_t *stream)
 	int rc = shapito_stream_ensure(stream, sizeof(shapito_header_t));
 	if (shapito_unlikely(rc == -1))
 		return -1;
-	shapito_stream_write8(stream, 'S');
+	shapito_stream_write8(stream, SHAPITO_FE_SYNC);
 	shapito_stream_write32(stream, sizeof(uint32_t));
 	return 0;
 }
diff --git a/shapito/macro.h b/shapito/macro.h
index 66778c3a..1ba218b7 100644
--- a/shapito/macro.h
+++ b/shapito/macro.h
@@ -9,14 +9,9 @@
 
 #define SHAPITO_API
 
-#define shapito_likely(expr) \
-	__builtin_expect(!! (expr), 1)
-
-#define shapito_unlikely(expr) \
-	__builtin_expect(!! (expr), 0)
-
-#define shapito_packed \
-   	__attribute__((packed))
+#define shapito_likely(expr)   __builtin_expect(!! (expr), 1)
+#define shapito_unlikely(expr) __builtin_expect(!! (expr), 0)
+#define shapito_packed         __attribute__((packed))
 
 #define shapito_container_of(ptr, type, field) \
 	((type*)((char*)(ptr) - __builtin_offsetof(type, field)))