diff --git a/tools/icons/makefile b/tools/icons/makefile
index c6018984ac..39e98985bb 100644
--- a/tools/icons/makefile
+++ b/tools/icons/makefile
@@ -1,3 +1,5 @@
+ICONFLAGS?=-g
+
 AD = ../..
 CXXFLAGS = -Wall
 CPPFLAGS = -I $(AD)/libs/gtkmm2ext -I $(AD)/libs/widgets -I $(AD)/libs/pbd -I $(AD)/build/libs/pbd
@@ -17,11 +19,15 @@ libwidgets:
 
 show: icon
 	rm -f /tmp/ardour_icons-*.png
-	./icon -g -s 22 -o /tmp/ardour_icons-22.png
-	./icon -g -s 23 -o /tmp/ardour_icons-23.png
-	./icon -g -s 44 -o /tmp/ardour_icons-44.png
-	./icon -g -s 45 -o /tmp/ardour_icons-45.png
-	convert -append /tmp/ardour_icons-*.png /tmp/ardour_icons.png
+	./icon $(ICONFLAGS) -s 22 -o /tmp/ardour_icons-22.png
+	./icon $(ICONFLAGS) -s 23 -o /tmp/ardour_icons-23.png
+	./icon $(ICONFLAGS) -s 44 -o /tmp/ardour_icons-44.png
+	./icon $(ICONFLAGS) -s 45 -o /tmp/ardour_icons-45.png
+	convert -gravity center \
+		/tmp/ardour_icons-*.png \
+		-background none \
+		+append /tmp/ardour_icons.png
+
 	display /tmp/ardour_icons.png &
 
 clean: