This commit is based on:
  https://github.com/zlib-ng/zlib-ng/commit/ca99a88

Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
---
 lib/zlib_deflate/deflate.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/lib/zlib_deflate/deflate.c b/lib/zlib_deflate/deflate.c
index 8a878d0d892c..f30d6b8a69b2 100644
--- a/lib/zlib_deflate/deflate.c
+++ b/lib/zlib_deflate/deflate.c
@@ -451,17 +451,24 @@ int zlib_deflate(
     Assert(strm->avail_out > 0, "bug2");
 
     if (flush != Z_FINISH) return Z_OK;
-    if (s->noheader) return Z_STREAM_END;
 
-    /* Write the zlib trailer (adler32) */
-    putShortMSB(s, (uInt)(strm->adler >> 16));
-    putShortMSB(s, (uInt)(strm->adler & 0xffff));
+    if (!s->noheader) {
+	/* Write zlib trailer (adler32) */
+	putShortMSB(s, (uInt)(strm->adler >> 16));
+	putShortMSB(s, (uInt)(strm->adler & 0xffff));
+    }
     flush_pending(strm);
     /* If avail_out is zero, the application will call deflate again
      * to flush the rest.
      */
-    s->noheader = -1; /* write the trailer only once! */
-    return s->pending != 0 ? Z_OK : Z_STREAM_END;
+    if (!s->noheader) {
+	s->noheader = -1; /* write the trailer only once! */
+    }
+    if (s->pending == 0) {
+	Assert(s->bi_valid == 0, "bi_buf not flushed");
+	return Z_STREAM_END;
+    }
+    return Z_OK;
 }
 
 /* ========================================================================= */
-- 
2.34.1