Index: trunk/src/org/openstreetmap/josm/gui/autofilter/AutoFilterRule.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/autofilter/AutoFilterRule.java	(revision 15842)
+++ trunk/src/org/openstreetmap/josm/gui/autofilter/AutoFilterRule.java	(revision 15843)
@@ -4,4 +4,5 @@
 import java.text.DecimalFormat;
 import java.util.Arrays;
+import java.util.Locale;
 import java.util.Objects;
 import java.util.Optional;
@@ -148,5 +149,5 @@
                 // #17109, support values like 0.5 or 1.5 - level values are multiplied by 2 when parsing, values are divided by 2 for formatting
                 .setValueExtractor(s -> (int) (Double.parseDouble(s) * 2.))
-                .setValueFormatter(v -> DecimalFormat.getInstance().format(v / 2.)),
+                .setValueFormatter(v -> DecimalFormat.getInstance(Locale.ROOT).format(v / 2.)),
             new AutoFilterRule("layer", 16)
                     .setDefaultValueSupplier(AutoFilterRule::defaultLayer),