diff --git a/libvips/arithmetic/arithmetic.c b/libvips/arithmetic/arithmetic.c
index 8fbb5fc6..570c9aa3 100644
--- a/libvips/arithmetic/arithmetic.c
+++ b/libvips/arithmetic/arithmetic.c
@@ -536,6 +536,8 @@ vips_arithmetic_gen( VipsRegion *or,
 
 	VIPS_GATE_STOP( "vips_arithmetic_gen: work" );
 
+	VIPS_COUNT_PIXELS( or, VIPS_OBJECT_CLASS( class )->nickname ); 
+
 	return( 0 );
 }