diff --git a/src/undo.c b/src/undo.c
index 998f3f3..d01ca9b 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -719,7 +719,7 @@
     char_u		*p;
 
     sha256_start(&ctx);
-    for (lnum = 1; lnum < curbuf->b_ml.ml_line_count; ++lnum)
+    for (lnum = 1; lnum <= curbuf->b_ml.ml_line_count; ++lnum)
     {
 	p = ml_get(lnum);
 	sha256_update(&ctx, p, (UINT32_T)(STRLEN(p) + 1));