diff --git a/common.h b/common.h
index 4f1c099..b818ceb 100644
--- a/common.h
+++ b/common.h
@@ -40,6 +40,7 @@
 #define STRINGIFY(x) #x
 #define EXPAND(x) STRINGIFY(x)
 
+extern bool modified_flash;
 typedef struct fstab_rec Volume;
 
 // fopen a file, mounting volumes and making parent dirs as necessary.