diff --git a/libuuu/fastboot.cpp b/libuuu/fastboot.cpp
index 640dd567..151cf0e9 100644
--- a/libuuu/fastboot.cpp
+++ b/libuuu/fastboot.cpp
@@ -845,7 +845,7 @@ int FBFlashCmd::run(CmdCtx *ctx)
 					nt.total = startblock;
 					call_notify(nt);
 
-				} while (off < pos);
+				} while (off + oldpos < pos);
 			}
 		}