diff --git a/400_xowa/src/gplx/xowa/xtns/gallery/Gallery_mgr_packed_base.java b/400_xowa/src/gplx/xowa/xtns/gallery/Gallery_mgr_packed_base.java
index 7ed681d07..b8259a905 100644
--- a/400_xowa/src/gplx/xowa/xtns/gallery/Gallery_mgr_packed_base.java
+++ b/400_xowa/src/gplx/xowa/xtns/gallery/Gallery_mgr_packed_base.java
@@ -45,8 +45,8 @@ public class Gallery_mgr_packed_base extends Gallery_mgr_base {
 		Get_thumb_size_static(lnki, ext, itm_default_w, itm_default_h);
 	}
 	@Override public void Adjust_image_parameters(Xof_file_itm xfer_itm) {
-		int w = (int)(xfer_itm.Html_w() / Scale_factor);
-		int h = (int)(xfer_itm.Html_h() / Scale_factor);
+		int w = (int)Math_.Ceil(xfer_itm.Html_w() / Scale_factor);
+		int h = (int)Math_.Ceil(xfer_itm.Html_h() / Scale_factor);
 		xfer_itm.Html_size_(w, h);
 	}
 	public static final double Scale_factor = 1.5d;	// We artificially have 1.5 the resolution neccessary so that we can scale it up by that much on the client side, without worrying about requesting a new image.
diff --git a/400_xowa/src/gplx/xowa/xtns/gallery/Gallery_mgr_packed_base__tst.java b/400_xowa/src/gplx/xowa/xtns/gallery/Gallery_mgr_packed_base__tst.java
new file mode 100644
index 000000000..7499949ed
--- /dev/null
+++ b/400_xowa/src/gplx/xowa/xtns/gallery/Gallery_mgr_packed_base__tst.java
@@ -0,0 +1,51 @@
+/*
+XOWA: the XOWA Offline Wiki Application
+Copyright (C) 2012-2017 gnosygnu@gmail.com
+
+XOWA is licensed under the terms of the General Public License (GPL) Version 3,
+or alternatively under the terms of the Apache License Version 2.0.
+
+You may use XOWA according to either of these licenses as is most appropriate
+for your project on a case-by-case basis.
+
+The terms of each license can be found in the source code repository:
+
+GPLv3 License: https://github.com/gnosygnu/xowa/blob/master/LICENSE-GPLv3.txt
+Apache License: https://github.com/gnosygnu/xowa/blob/master/LICENSE-APACHE2.txt
+*/
+package gplx.xowa.xtns.gallery; import gplx.*; import gplx.xowa.*; import gplx.xowa.xtns.*;
+import org.junit.*; import gplx.core.tests.*;
+import gplx.xowa.files.*;
+import gplx.xowa.parsers.lnkis.*;
+public class Gallery_mgr_packed_base__tst {
+	private final    Gallery_mgr_packed_base__fxt fxt = new Gallery_mgr_packed_base__fxt();
+	@Test  public void Get_thumb_size_static() {
+		fxt.Test__Get_thumb_size_static(Xof_ext_.Id_png, 300, 200, fxt.Make__lnki(4650, 450));
+	}
+	@Test  public void Adjust_image_parameters() {// PURPOSE: use ceil; ISSUE#:640; DATE:2020-01-08
+		fxt.Test__Adjust_image_parameters(fxt.Make__file(4, 4), 3, 3); // fails if 2, 2
+	}
+}
+class Gallery_mgr_packed_base__fxt {
+	public Xop_lnki_tkn Make__lnki(int w, int h) {
+		return new Xop_lnki_tkn().W_(w).H_(h);
+	}
+	public Xof_file_itm Make__file(int w, int h) {
+		Xof_fsdb_itm rv = new Xof_fsdb_itm();
+		rv.Html_size_(w, h);
+		return rv;
+	}
+	public void Test__Get_thumb_size_static(int ext_id, int itm_default_w, int itm_default_h, Xop_lnki_tkn expd) {
+		Xof_ext ext = Xof_ext_.new_by_id_(ext_id);
+		Xop_lnki_tkn actl = new Xop_lnki_tkn();
+		Gallery_mgr_packed_base.Get_thumb_size_static(actl, ext, itm_default_w, itm_default_w);
+		Gftest.Eq__int(expd.W(), actl.W());
+		Gftest.Eq__int(expd.H(), actl.H());
+	}
+	public void Test__Adjust_image_parameters(Xof_file_itm xfer_itm, int expd_w, int expd_h) {
+		Gallery_mgr_packed_base mgr = new Gallery_mgr_packed_base();
+		mgr.Adjust_image_parameters(xfer_itm);
+		Gftest.Eq__int(expd_w, xfer_itm.Html_w());
+		Gftest.Eq__int(expd_h, xfer_itm.Html_h());
+	}
+}