diff --git a/docs/support-matrix-generate b/docs/support-matrix-generate
index a3d93321f190..8a27849cf6a4 100755
--- a/docs/support-matrix-generate
+++ b/docs/support-matrix-generate
@@ -27,8 +27,8 @@
 #
 # Then we try to find the next previous revision.  This is done by
 # extracting the current version number from xen/Makefile.  (We make
-# some slight assumption about how xen/Makefile's xenversion target
-# works, because we want to be able to do this without checking out
+# some slight assumption about how xen/Makefile's variables are
+# written, because we want to be able to do this without checking out
 # the whole tree for the version in question.)  Then we use git log on
 # xen/Makefile to try to find a commit where the version changed.
 # This gives us the previous version number, NN.
@@ -102,12 +102,16 @@ commitish_version () {
     esac
 
     git cat-file blob "$commitish:$versionfile" >"$tmp_versionfile"
-    version=$(make --no-print-directory -C docs \
-                   -f "${tmp_versionfile#docs/}" xenversion)
-    case "$version" in
-        *.*.*) version="${version%.*}" ;;
-    esac
-    printf "%s\n" "${version%%-*}"
+
+    local maj=$(sed -n 's/.*XEN_VERSION.*= \([0-9]\+\)/\1/p' < "$tmp_versionfile")
+    local min=$(sed -n 's/.*XEN_SUBVERSION.*= \([0-9]\+\)/\1/p' < "$tmp_versionfile")
+
+    if [ -z $maj ] || [ -z $min ];
+    then
+        fail "Unable to identify Xen version for $commitish";
+    fi
+
+    printf "%d.%d\n" "$maj" "$min"
 }
 
 exec 4>"$tmp_revisions"