diff --git a/mavros/src/plugins/ftp.cpp b/mavros/src/plugins/ftp.cpp
index 8cd46b62a..8a60c69e8 100644
--- a/mavros/src/plugins/ftp.cpp
+++ b/mavros/src/plugins/ftp.cpp
@@ -531,7 +531,7 @@ class FTPPlugin : public MavRosPlugin {
 		const size_t bytes_to_copy = write_bytes_to_copy();
 		if (bytes_to_copy > 0) {
 			// More data to write
-			write_offset += bytes_to_copy;
+			write_offset += hdr->size;
 			send_write_command(bytes_to_copy);
 		}
 		else