diff --git a/libsrc/mosaicing/yafrsmooth.cpp b/libsrc/mosaicing/yafrsmooth.cpp
index 5f3a8335..5b002959 100644
--- a/libsrc/mosaicing/yafrsmooth.cpp
+++ b/libsrc/mosaicing/yafrsmooth.cpp
@@ -128,6 +128,14 @@
  */
 #define SMOOTH_SHARPENING_SCALE (0.453125f)
 
+/* Properties.
+ */
+enum {
+	PROP_SHARPENING = 1,
+	PROP_LAST
+};
+
+
 #define VIPS_TYPE_INTERPOLATE_YAFRSMOOTH \
 	(vips_interpolate_yafrsmooth_get_type())
 #define VIPS_INTERPOLATE_YAFRSMOOTH( obj ) \
@@ -745,6 +753,8 @@ vips_interpolate_yafrsmooth_class_init( VipsInterpolateYafrsmoothClass *iclass )
 	VipsInterpolateClass *interpolate_class = 
 		VIPS_INTERPOLATE_CLASS( iclass );
 
+	GParamSpec *pspec;
+
 	gobject_class->set_property = vips_object_set_property;
 	gobject_class->get_property = vips_object_get_property;
 
@@ -766,6 +776,19 @@ vips_interpolate_yafrsmooth_class_init( VipsInterpolateYafrsmoothClass *iclass )
 			iclass->matrixi[x][i] = 
 				iclass->matrixf[x][i] * VIPS_INTERPOLATE_SCALE;
 	}
+
+	/* Create properties.
+	 */
+	pspec = g_param_spec_double( "sharpening", 
+		_( "Sharpening" ),
+		_( "Degree of extra edge enhancement" ),
+		0, 4, 1, 
+		(GParamFlags) G_PARAM_READWRITE );
+	g_object_class_install_property( gobject_class, 
+		PROP_SHARPENING, pspec );
+	vips_object_class_install_argument( object_class, pspec,
+		VIPS_ARGUMENT_SET_ONCE,
+		G_STRUCT_OFFSET( VipsInterpolateYafrsmooth, sharpening ) );
 }
 
 static void