diff --git a/src/grep.c b/src/grep.c

--- a/src/grep.c

+++ b/src/grep.c

@@ -1415,13 +1415,13 @@ grep (int fd, struct stat const *st)

         }

       /* Detect whether leading context is adjacent to previous output.  */

-      if (lastout)

-        {

-          if (textbin == TEXTBIN_UNKNOWN)

-            textbin = TEXTBIN_TEXT;

-          if (beg != lastout)

-            lastout = 0;

-        }

+      if (beg != lastout)

+        lastout = 0;

+

+      /* If the file's textbin has not been determined yet, assume

+         it's text if has found any matched line already.  */

+      if (textbin == TEXTBIN_UNKNOWN && nlines)

+        textbin = TEXTBIN_TEXT;

       /* Handle some details and read more data to scan.  */

       save = residue + lim - beg;