diff --git a/R/tmapGridAux.R b/R/tmapGridAux.R
index f85682e8..47f9634f 100644
--- a/R/tmapGridAux.R
+++ b/R/tmapGridAux.R
@@ -88,10 +88,10 @@ tmapGridTilesPrep = function(a, bs, id, o) {
 		d = s$dt
 		d[, c("col", "legnr", "crtnr") := do.call(srgb$FUN, list(x1 = red, x2 = green, x3 = blue, scale = srgb, legend = list(), o = o, aes = "col", layer = "raster", sortRev = NA, bypass_ord = TRUE))]
 		if ("alpha" %in% names(d)) {
-			d[, col_alpha:=alpha/255]
+			d[, col_alpha:=alpha/255 * a$alpha]
 			d[is.na(col_alpha), col_alpha:=0]
 		} else {
-			d[, col_alpha:=1L]
+			d[, col_alpha:=a$alpha]
 		}
 		d
 	})