diff --git a/render.h b/render.h
index 8ae2e42..5838246 100644
--- a/render.h
+++ b/render.h
@@ -17,7 +17,7 @@
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL SuSE
  * BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
- * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN 
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  *
  * Author:  Keith Packard, SuSE, Inc.
@@ -163,6 +163,8 @@ typedef unsigned long	PictFormat;
 #define FilterGood			    "good"
 #define FilterBest			    "best"
 
+#define FilterConvolution		    "convolution"
+
 #define FilterAliasNone			    -1
 
 /* Subpixel orders included in 0.6 */