diff --git a/nmap.spec b/nmap.spec
index 91d8ffa..2c84c44 100644
--- a/nmap.spec
+++ b/nmap.spec
@@ -2,7 +2,7 @@
 Summary: Network exploration tool and security scanner
 Name: nmap
 Version: 5.21
-Release: 9%{?dist}
+Release: 10%{?dist}
 # nmap is GPLv2
 # zenmap is GPLv2 and LGPLv2+ (zenmap/higwidgets) and GPLv2+ (zenmap/radialnet)
 # libdnet-stripped is BSD (advertising clause rescinded by the Univ. of California in 1999) with some parts as Public Domain (crc32)
@@ -24,6 +24,9 @@ Patch2: nmap-4.52-noms.patch
 #don't strip debuginfo
 Patch3: nmap-4.68-nostrip.patch
 
+# rhbz#637403, workaround for rhbz#621887=gnome#623965
+Patch4: zenmap-621887-workaround.patch
+
 URL: http://nmap.org/
 BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)
 Epoch: 2
@@ -55,6 +58,7 @@ be installed before installing nmap front end.
 %patch1 -p1 -b .mktemp
 %patch2 -p1 -b .noms
 %patch3 -p1 -b .nostrip
+%patch4 -p1 -b .bz637403
 
 #be sure we're not using tarballed copies of some libraries
 rm -rf liblua libpcap libpcre macosx mswin32
@@ -165,6 +169,9 @@ rm -rf $RPM_BUILD_ROOT
 %{_mandir}/man1/xnmap.1.gz
 
 %changelog
+* Tue Oct 05 2010 Michal Hlavinka <mhlavink@redhat.com> - 2:5.21-10
+- add workaround for zenmap crash (#637403)
+
 * Wed Sep 29 2010 jkeating - 2:5.21-9
 - Rebuilt for gcc bug 634757
 
diff --git a/zenmap-621887-workaround.patch b/zenmap-621887-workaround.patch
new file mode 100644
index 0000000..aba22b7
--- /dev/null
+++ b/zenmap-621887-workaround.patch
@@ -0,0 +1,21 @@
+diff -uNrp nmap-5.21.orig/zenmap/zenmapGUI/App.py nmap-5.21.new/zenmap/zenmapGUI/App.py
+--- nmap-5.21.orig/zenmap/zenmapGUI/App.py	2009-11-04 04:36:50.000000000 +0100
++++ nmap-5.21.new/zenmap/zenmapGUI/App.py	2010-09-25 15:45:20.000000000 +0200
+@@ -96,7 +96,7 @@ import ConfigParser
+ # produces a warning, but the lack of a display eventually causes a
+ # segmentation fault. See http://live.gnome.org/PyGTK/WhatsNew210.
+ import warnings
+-warnings.filterwarnings("error", module = "gtk")
++warnings.filterwarnings("error", module = "gtk", append=True)
+ try:
+     import gtk
+ except Exception:
+@@ -176,7 +176,7 @@ def install_excepthook():
+         # produces a warning, but the lack of a display eventually causes a
+         # segmentation fault. See http://live.gnome.org/PyGTK/WhatsNew210.
+         import warnings
+-        warnings.filterwarnings("error", module = "gtk")
++        warnings.filterwarnings("error", module = "gtk", append=True)
+         import gtk
+         warnings.resetwarnings()
+