diff --git a/tools/Rules.mk b/tools/Rules.mk
index 2907ed2d39..b022da3336 100644
--- a/tools/Rules.mk
+++ b/tools/Rules.mk
@@ -6,6 +6,11 @@ all:
 -include $(XEN_ROOT)/config/Tools.mk
 include $(XEN_ROOT)/Config.mk
 
+XEN_FULLVERSION=$(shell env \
+    XEN_EXTRAVERSION=$(XEN_EXTRAVERSION) \
+    XEN_VENDORVERSION=$(XEN_VENDORVERSION) \
+    $(SHELL) $(XEN_ROOT)/version.sh --full $(XEN_ROOT)/xen/Makefile)
+
 export _INSTALL := $(INSTALL)
 INSTALL = $(XEN_ROOT)/tools/cross-install
 
diff --git a/tools/flask/policy/Makefile.common b/tools/flask/policy/Makefile.common
index bea5ba4b6a..e5ed58200e 100644
--- a/tools/flask/policy/Makefile.common
+++ b/tools/flask/policy/Makefile.common
@@ -35,7 +35,7 @@ OUTPUT_POLICY ?= $(BEST_POLICY_VER)
 #
 ########################################
 
-POLICY_FILENAME = $(FLASK_BUILD_DIR)/xenpolicy-$(shell $(MAKE) -C $(XEN_ROOT)/xen xenversion --no-print-directory)
+POLICY_FILENAME = $(FLASK_BUILD_DIR)/xenpolicy-$(XEN_FULLVERSION)
 POLICY_LOADPATH = /boot
 
 # List of policy versions supported by the hypervisor
diff --git a/version.sh b/version.sh
index e894ee7e04..c6a5692c19 100755
--- a/version.sh
+++ b/version.sh
@@ -1,5 +1,21 @@
 #!/bin/sh
 
+opt_full=false
+while [ $# -gt 1 ]; do
+    case "$1" in
+        --full) opt_full=true ;;
+        *) break ;;
+    esac
+    shift
+done
+
 MAJOR=`grep "export XEN_VERSION" $1 | sed 's/.*=//g' | tr -s " "`
 MINOR=`grep "export XEN_SUBVERSION" $1 | sed 's/.*=//g' | tr -s " "`
-printf "%d.%d" $MAJOR $MINOR
+
+if $opt_full; then
+    extraversion=$(grep "export XEN_EXTRAVERSION" $1 | sed 's/^.* ?=\s\+//; s/\$([^)]*)//g; s/ //g')
+    : ${XEN_EXTRAVERSION:=${extraversion}${XEN_VENDORVERSION}}
+else
+    unset XEN_EXTRAVERSION
+fi
+printf "%d.%d%s" $MAJOR $MINOR $XEN_EXTRAVERSION