diff --git a/libedit-20120601-3.0-insertstr-mb.patch b/libedit-20120601-3.0-insertstr-mb.patch
new file mode 100644
index 0000000..94102d8
--- /dev/null
+++ b/libedit-20120601-3.0-insertstr-mb.patch
@@ -0,0 +1,27 @@
+From 73a91fafe8da0a1e8905280e8fa861a5d1d0e698 Mon Sep 17 00:00:00 2001
+From: Kamil Dudka <kdudka@redhat.com>
+Date: Wed, 18 Jul 2012 14:11:55 +0200
+Subject: [PATCH] fix crash of el_insertstr() on incomplete multi-byte
+ sequence
+
+https://bugzilla.redhat.com/840598
+---
+ src/chared.c |    2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/src/chared.c b/src/chared.c
+index f816d89..d3b0f22 100644
+--- a/src/chared.c
++++ b/src/chared.c
+@@ -612,7 +612,7 @@ FUN(el,insertstr)(EditLine *el, const Char *s)
+ {
+ 	size_t len;
+ 
+-	if ((len = Strlen(s)) == 0)
++	if (s == NULL || (len = Strlen(s)) == 0)
+ 		return -1;
+ 	if (el->el_line.lastchar + len >= el->el_line.limit) {
+ 		if (!ch_enlargebufs(el, len))
+-- 
+1.7.10.4
+
diff --git a/libedit.spec b/libedit.spec
index 2f57d84..425157a 100644
--- a/libedit.spec
+++ b/libedit.spec
@@ -9,6 +9,9 @@ Group:		System Environment/Libraries
 URL:		http://www.thrysoee.dk/editline/
 Source0:	http://www.thrysoee.dk/editline/%{name}-%{snap}-%{version}.tar.gz
 
+# fix crash of el_insertstr() on incomplete multi-byte sequence (#840598)
+Patch0:		libedit-20120601-3.0-insertstr-mb.patch
+
 BuildRequires:	ncurses-devel
 
 %description
@@ -29,6 +32,7 @@ This package contains development files for %{name}.
 
 %prep
 %setup -q -n %{name}-%{snap}-%{version}
+%patch0 -p1
 
 # Suppress rpmlint error.
 iconv -f ISO8859-1 -t UTF-8 -o ChangeLog.utf-8 ChangeLog
@@ -76,6 +80,7 @@ rm -rf $RPM_BUILD_ROOT
 %changelog
 * Wed Jul 18 2012 Kamil Dudka <kdudka@redhat.com> 3.0-7.20120601cvs
 - Update to 3.0 (20120601 snap)
+- fix crash of el_insertstr() on incomplete multi-byte sequence (#840598)
 
 * Fri Jan 13 2012 Fedora Release Engineering <rel-eng@lists.fedoraproject.org> - 3.0-6.20110802cvs
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_17_Mass_Rebuild