diff --git a/pdb-plotting/src/main/java/org/lucares/pdb/plot/api/BarChartAggregatorForIntervals.java b/pdb-plotting/src/main/java/org/lucares/pdb/plot/api/BarChartAggregatorForIntervals.java
index 11b8f58..2dba195 100644
--- a/pdb-plotting/src/main/java/org/lucares/pdb/plot/api/BarChartAggregatorForIntervals.java
+++ b/pdb-plotting/src/main/java/org/lucares/pdb/plot/api/BarChartAggregatorForIntervals.java
@@ -75,7 +75,7 @@ public class BarChartAggregatorForIntervals implements CustomAggregator, Indexed
         int offset = 0;
         for (final String bucketId : bucketIds()) {
             final long count = buckets.get(bucketId).get();
-            csv.append(offset + getIndex() * SPACE_BETWEEN_BARS + 0.5);
+            csv.append(String.format(Locale.US, "%f", offset + getIndex() * SPACE_BETWEEN_BARS + 0.5));
             csv.append(",");
             csv.append(renderLabels && isMiddleSeries ? bucketId : "");
             csv.append(",");
@@ -115,7 +115,7 @@ public class BarChartAggregatorForIntervals implements CustomAggregator, Indexed
         int offset = 0;
         for (final String bucketId : bucketIds()) {
             final long count = buckets.get(bucketId).get();
-            final String label = String.format("set label at %s %f, %d '%s' center front offset 0,0.3\n", // front
+            final String label = String.format(Locale.US, "set label at %s %f, %d '%s' center front offset 0,0.3\n", // front
                     xAxis == GnuplotAxis.X1 ? "first" : "second", //
                     offset + getIndex() * SPACE_BETWEEN_BARS + 0.5, // x-axis position of the label
                     count, // y axis position of the label