diff --git a/yap-6.2.2-Off-by-one-error-when-initializing-yap_flags.patch b/yap-6.2.2-Off-by-one-error-when-initializing-yap_flags.patch
new file mode 100644
index 0000000..a376743
--- /dev/null
+++ b/yap-6.2.2-Off-by-one-error-when-initializing-yap_flags.patch
@@ -0,0 +1,41 @@
+From fa8f0f7b2d107770ae4d37bc77c902eafc59c86c Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Petr=20P=C3=ADsa=C5=99?= <ppisar@redhat.com>
+Date: Mon, 7 Jan 2013 17:31:08 +0100
+Subject: [PATCH] Off-by-one error when initializing yap_flags
+
+The yap_flags_field of all_heap_codes structure is of type
+Int[LAST_FLAG], thus the loop should iterate from 0 to LAST_FLAG - 1.
+---
+ C/init.c     | 2 +-
+ C/stdpreds.c | 2 +-
+ 2 files changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/C/init.c b/C/init.c
+index dda09cc..8f01864 100755
+--- a/C/init.c
++++ b/C/init.c
+@@ -1348,7 +1348,7 @@ Yap_InitWorkspace(UInt Heap, UInt Stack, UInt Trail, UInt Atts, UInt max_table_s
+   Yap_InitTime ();
+   /* InitAbsmi must be done before InitCodes */
+   /* This must be done before initialising predicates */
+-  for (i = 0; i <= LAST_FLAG; i++) {
++  for (i = 0; i < LAST_FLAG; i++) {
+     yap_flags[i] = 0;
+   }
+ #ifdef MPW
+diff --git a/C/stdpreds.c b/C/stdpreds.c
+index a4c0e86..8a4183f 100755
+--- a/C/stdpreds.c
++++ b/C/stdpreds.c
+@@ -3637,7 +3637,7 @@ p_access_yap_flags(void)
+     return(FALSE);		
+   }
+   flag = IntOfTerm(tflag);
+-  if (flag < 0 || flag > NUMBER_OF_YAP_FLAGS) {
++  if (flag < 0 || flag >= NUMBER_OF_YAP_FLAGS) {
+     return(FALSE);
+   }
+ #ifdef TABLING
+-- 
+1.7.11.7
+
diff --git a/yap.spec b/yap.spec
index f63fde3..205b107 100644
--- a/yap.spec
+++ b/yap.spec
@@ -4,7 +4,7 @@
 
 Name:       yap
 Version:    6.2.2
-Release:    3%{?dist}
+Release:    4%{?dist}
 Summary:    High-performance Prolog Compiler
 Group:      Development/Languages
 # README                            Perl Artistic license 2 and the FSF's LGPL
@@ -27,6 +27,8 @@ Patch7:     yap-6.2.0-Do-not-install-info-dir-index.patch
 Patch8:     yap-6.2.0-gprof-macro.patch
 # Fix compilation of PLStream package on PPC
 Patch9:     yap-6.2.0-Remove-feature-macro.patch
+# Reported to upstream <yap-users@lists.sourceforge.net>
+Patch10:    yap-6.2.2-Off-by-one-error-when-initializing-yap_flags.patch
 # yap 6.2.2 does not work on PPC (bug #790625)
 ExcludeArch:    ppc ppc64
 BuildRequires:  autoconf
@@ -83,6 +85,7 @@ Documentation for Yap.
 %patch7 -p1 -b .do_not_install_info_index
 %patch8 -p1 -b .macro
 %patch9 -p1 -b .remove_feature_macro
+%patch10 -p1 -b .initialization
 
 # remove redundant RPATH
 sed -i 's/-Wl,-R\(,\)\{0,1\}\\$(LIBDIR)//' configure.in
@@ -223,6 +226,9 @@ fi
 
 
 %changelog
+* Mon Jan 07 2013 Petr Pisar <ppisar@redhat.com> - 6.2.2-4
+- Fix off-by-one error when initializing yap_flags
+
 * Thu Feb 23 2012 Petr Pisar <ppisar@redhat.com> - 6.2.2-3
 - yap 6.2.2 does not work on PPC (bug #790625)