diff --git a/src/connection.c b/src/connection.c
index d05341aa..40a21826 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -512,7 +512,7 @@ wl_closure_marshal(struct wl_object *sender, uint32_t opcode,
 
 	count = arg_count_for_signature(message->signature);
 	if (count > WL_CLOSURE_MAX_ARGS) {
-		printf("too many args (%d)\n", count);
+		wl_log("too many args (%d)\n", count);
 		errno = EINVAL;
 		return NULL;
 	}
@@ -557,13 +557,13 @@ wl_closure_marshal(struct wl_object *sender, uint32_t opcode,
 			fd = args[i].h;
 			dup_fd = wl_os_dupfd_cloexec(fd, 0);
 			if (dup_fd < 0) {
-				fprintf(stderr, "dup failed: %m");
+				wl_log("dup failed: %m");
 				abort();
 			}
 			closure->args[i].h = dup_fd;
 			break;
 		default:
-			fprintf(stderr, "unhandled format code: '%c'\n",
+			wl_log("unhandled format code: '%c'\n",
 				arg.type);
 			assert(0);
 			break;
@@ -615,7 +615,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 
 	count = arg_count_for_signature(message->signature);
 	if (count > WL_CLOSURE_MAX_ARGS) {
-		printf("too many args (%d)\n", count);
+		wl_log("too many args (%d)\n", count);
 		errno = EINVAL;
 		wl_connection_consume(connection, size);
 		return NULL;
@@ -642,7 +642,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 		signature = get_next_argument(signature, &arg);
 
 		if (arg.type != 'h' && p + 1 > end) {
-			printf("message too short, "
+			wl_log("message too short, "
 			       "object (%d), message %s(%s)\n",
 			       *p, message->name, message->signature);
 			errno = EINVAL;
@@ -669,7 +669,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 
 			next = p + DIV_ROUNDUP(length, sizeof *p);
 			if (next > end) {
-				printf("message too short, "
+				wl_log("message too short, "
 				       "object (%d), message %s(%s)\n",
 				       closure->sender_id, message->name,
 				       message->signature);
@@ -680,7 +680,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 			s = (char *) p;
 
 			if (length > 0 && s[length - 1] != '\0') {
-				printf("string not nul-terminated, "
+				wl_log("string not nul-terminated, "
 				       "message %s(%s)\n",
 				       message->name, message->signature);
 				errno = EINVAL;
@@ -695,7 +695,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 			closure->args[i].n = id;
 
 			if (id == 0 && !arg.nullable) {
-				printf("NULL object received on non-nullable "
+				wl_log("NULL object received on non-nullable "
 				       "type, message %s(%s)\n", message->name,
 				       message->signature);
 				errno = EINVAL;
@@ -707,7 +707,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 			closure->args[i].n = id;
 
 			if (id == 0 && !arg.nullable) {
-				printf("NULL new ID received on non-nullable "
+				wl_log("NULL new ID received on non-nullable "
 				       "type, message %s(%s)\n", message->name,
 				       message->signature);
 				errno = EINVAL;
@@ -715,7 +715,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 			}
 
 			if (wl_map_reserve_new(objects, id) < 0) {
-				printf("not a valid new object id (%d), "
+				wl_log("not a valid new object id (%d), "
 				       "message %s(%s)\n",
 				       id, message->name, message->signature);
 				errno = EINVAL;
@@ -728,7 +728,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 
 			next = p + DIV_ROUNDUP(length, sizeof *p);
 			if (next > end) {
-				printf("message too short, "
+				wl_log("message too short, "
 				       "object (%d), message %s(%s)\n",
 				       closure->sender_id, message->name,
 				       message->signature);
@@ -745,7 +745,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 			break;
 		case 'h':
 			if (connection->fds_in.tail == connection->fds_in.head) {
-				printf("file descriptor expected, "
+				wl_log("file descriptor expected, "
 				       "object (%d), message %s(%s)\n",
 				       closure->sender_id, message->name,
 				       message->signature);
@@ -758,7 +758,7 @@ wl_connection_demarshal(struct wl_connection *connection,
 			closure->args[i].h = fd;
 			break;
 		default:
-			printf("unknown type\n");
+			wl_log("unknown type\n");
 			assert(0);
 			break;
 		}
@@ -817,7 +817,7 @@ wl_closure_lookup_objects(struct wl_closure *closure, struct wl_map *objects)
 				 * destroyed client side */
 				object = NULL;
 			} else if (object == NULL && id != 0) {
-				printf("unknown object (%u), message %s(%s)\n",
+				wl_log("unknown object (%u), message %s(%s)\n",
 				       id, message->name, message->signature);
 				object = NULL;
 				errno = EINVAL;
@@ -827,7 +827,7 @@ wl_closure_lookup_objects(struct wl_closure *closure, struct wl_map *objects)
 			if (object != NULL && message->types[i] != NULL &&
 			    !wl_interface_equal((object)->interface,
 						message->types[i])) {
-				printf("invalid object (%u), type (%s), "
+				wl_log("invalid object (%u), type (%s), "
 				       "message %s(%s)\n",
 				       id, (object)->interface->name,
 				       message->name, message->signature);
@@ -893,7 +893,7 @@ convert_arguments_to_ffi(const char *signature, uint32_t flags,
 			ffi_args[i] = &args[i].h;
 			break;
 		default:
-			printf("unknown type\n");
+			wl_log("unknown type\n");
 			assert(0);
 			break;
 		}
@@ -953,8 +953,8 @@ copy_fds_to_connection(struct wl_closure *closure,
 
 		fd = closure->args[i].h;
 		if (wl_connection_put_fd(connection, fd)) {
-			fprintf(stderr, "request could not be marshaled: "
-				"can't send file descriptor");
+			wl_log("request could not be marshaled: "
+			       "can't send file descriptor");
 			return -1;
 		}
 	}