diff --git a/tools/applypatch/applypatch.h b/tools/applypatch/applypatch.h
index 041ac2e..e0320fb 100644
--- a/tools/applypatch/applypatch.h
+++ b/tools/applypatch/applypatch.h
@@ -38,6 +38,11 @@
 // and use it as the source instead.
 #define CACHE_TEMP_SOURCE "/cache/saved.file"
 
+// When writing to an MTD partition, we first put the output in this
+// temp file, then copy it to the partition once the patching is
+// finished (and the target sha1 verified).
+#define MTD_TARGET_TEMP_FILE "/tmp/mtd-temp"
+
 // applypatch.c
 size_t FreeSpaceForFile(const char* filename);