diff --git a/librz/include/rz_io.h b/librz/include/rz_io.h
index 934a3f03340..51c3de97295 100644
--- a/librz/include/rz_io.h
+++ b/librz/include/rz_io.h
@@ -333,7 +333,7 @@ RZ_API bool rz_io_write(RzIO *io, const ut8 *buf, size_t len);
 RZ_API ut64 rz_io_size(RzIO *io);
 RZ_API bool rz_io_is_listener(RzIO *io);
 RZ_API char *rz_io_system(RzIO *io, const char *cmd);
-RZ_API bool rz_io_resize(RzIO *io, ut64 newsize);
+RZ_API bool rz_io_resize(RZ_NONNULL RzIO *io, ut64 newsize);
 RZ_API bool rz_io_extend_at(RzIO *io, ut64 addr, ut64 size);
 RZ_API bool rz_io_set_write_mask(RzIO *io, const ut8 *mask, size_t len);
 RZ_API void rz_io_bind(RzIO *io, RzIOBind *bnd);
diff --git a/librz/io/io.c b/librz/io/io.c
index 24ef79ea7a2..f5edea44a7b 100644
--- a/librz/io/io.c
+++ b/librz/io/io.c
@@ -422,27 +422,25 @@ RZ_API char *rz_io_system(RzIO *io, const char *cmd) {
 	return NULL;
 }
 
-RZ_API bool rz_io_resize(RzIO *io, ut64 newsize) {
-	if (io) {
-		RzList *maps = rz_io_map_get_for_fd(io, io->desc->fd);
-		RzIOMap *current_map;
-		RzListIter *iter;
-		ut64 fd_size = rz_io_fd_size(io, io->desc->fd);
-		bool ret = rz_io_desc_resize(io->desc, newsize);
-		if (!ret) {
-			rz_list_free(maps);
-			return false;
-		}
-		rz_list_foreach (maps, iter, current_map) {
-			// we just resize map of the same size of its fd
-			if (current_map->itv.size == fd_size) {
-				rz_io_map_resize(io, current_map->id, newsize);
-			}
-		}
+RZ_API bool rz_io_resize(RZ_NONNULL RzIO *io, ut64 newsize) {
+	rz_return_val_if_fail(io && io->desc, false);
+
+	RzList *maps = rz_io_map_get_for_fd(io, io->desc->fd);
+	ut64 fd_size = rz_io_fd_size(io, io->desc->fd);
+	if (!rz_io_desc_resize(io->desc, newsize)) {
 		rz_list_free(maps);
-		return true;
+		return false;
 	}
-	return false;
+	RzListIter *iter;
+	RzIOMap *current_map;
+	rz_list_foreach (maps, iter, current_map) {
+		// we just resize map of the same size of its fd
+		if (current_map->itv.size == fd_size) {
+			rz_io_map_resize(io, current_map->id, newsize);
+		}
+	}
+	rz_list_free(maps);
+	return true;
 }
 
 RZ_API bool rz_io_close(RzIO *io) {