diff --git a/src/cairo-fixed-private.h b/src/cairo-fixed-private.h
index 75ecc06dc..b30879438 100644
--- a/src/cairo-fixed-private.h
+++ b/src/cairo-fixed-private.h
@@ -165,6 +165,12 @@ _cairo_fixed_integer_round (cairo_fixed_t f)
     return (f + (CAIRO_FIXED_FRAC_MASK+1)/2) >> CAIRO_FIXED_FRAC_BITS;
 }
 
+static inline int
+_cairo_fixed_integer_round_down (cairo_fixed_t f)
+{
+    return (f + CAIRO_FIXED_FRAC_MASK/2) >> CAIRO_FIXED_FRAC_BITS;
+}
+
 static inline int
 _cairo_fixed_fractional_part (cairo_fixed_t f)
 {
diff --git a/src/cairo-image-surface.c b/src/cairo-image-surface.c
index a6953fb1b..b2b69d372 100644
--- a/src/cairo-image-surface.c
+++ b/src/cairo-image-surface.c
@@ -2864,10 +2864,11 @@ _composite_boxes (cairo_image_surface_t *dst,
 	    cairo_box_t *box = chunk->base;
 
 	    for (i = 0; i < chunk->count; i++) {
-		int x1 = _cairo_fixed_integer_round (box[i].p1.x);
-		int y1 = _cairo_fixed_integer_round (box[i].p1.y);
-		int x2 = _cairo_fixed_integer_round (box[i].p2.x);
-		int y2 = _cairo_fixed_integer_round (box[i].p2.y);
+                /* round down here to match Pixman's behavior when using traps. */
+		int x1 = _cairo_fixed_integer_round_down (box[i].p1.x);
+		int y1 = _cairo_fixed_integer_round_down (box[i].p1.y);
+		int x2 = _cairo_fixed_integer_round_down (box[i].p2.x);
+		int y2 = _cairo_fixed_integer_round_down (box[i].p2.y);
 
 		if (x2 == x1 || y2 == y1)
 		    continue;