diff --git a/src/mobile-config-firefox.sh b/src/mobile-config-firefox.sh
index 57be005..842395c 100644
--- a/src/mobile-config-firefox.sh
+++ b/src/mobile-config-firefox.sh
@@ -12,20 +12,28 @@ prepare_profile() {
 	fi
 }
 
-profile_found=false
-for profiledir in ~/.mozilla/firefox/*/; do
-	if ! [ -e "$profiledir/prefs.js" ]; then
-		continue
-	fi
+if [ -e ~/.mozilla/firefox/profiles.ini ]; then
+	# Firefox was started without this wrapper and created profiles.ini.
+	# Add the userChrome.css symlink to all existing profiles, then let
+	# firefox run with the default profile.
 
-	prepare_profile "$profiledir"
-	profile_found=true
-done
+	for profiledir in ~/.mozilla/firefox/*/; do
+		if ! [ -e "$profiledir/prefs.js" ]; then
+			continue
+		fi
+
+		prepare_profile "$profiledir"
+	done
 
-if [ "$profile_found" = "true" ]; then
 	exec /usr/bin/firefox "$@"
 else
+	# Firefox was not started without this wrapper. Create a profile dir
+	# called "firefox.default" if it does not exist yet, and add the
+	# userChrome.css symlink. Let firefox use this profile. It will not
+	# create the profiles.ini file.
+
 	profiledir=~/.mozilla/firefox/firefox.default
 	prepare_profile "$profiledir"
+
 	exec /usr/bin/firefox --profile "$profiledir" "$@"
 fi