diff --git a/src/memline.c b/src/memline.c
index 06fd97c..c18109a 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -5778,7 +5778,7 @@
 	     && lnum >= curline + buf->b_ml.ml_chunksize[curix].mlcs_numlines)
 		|| (offset != 0
 	       && offset > size + buf->b_ml.ml_chunksize[curix].mlcs_totalsize
-		      + ffdos * buf->b_ml.ml_chunksize[curix].mlcs_numlines)))
+		 + (long)ffdos * buf->b_ml.ml_chunksize[curix].mlcs_numlines)))
     {
 	curline += buf->b_ml.ml_chunksize[curix].mlcs_numlines;
 	size += buf->b_ml.ml_chunksize[curix].mlcs_totalsize;