diff --git a/postprocess.sh b/postprocess.sh
index 82ea454..f44cb52 100755
--- a/postprocess.sh
+++ b/postprocess.sh
@@ -32,11 +32,11 @@ for date in "${dates[@]}"; do
 
     if [[ -z "$alt_text" ]]; then
         convert "$image_in" \
-            -background white -alpha background \
+            -background white -alpha remove -alpha off \
             "$image_out"
     else
         convert "$image_in" \
-            -background white -alpha background \
+            -background white -alpha remove -alpha off \
             -gravity center \
             -pointsize 12 -size 360x caption:"$alt_text" \
             -append \