diff --git a/jni/testfixtures/app/opendocument/core/TestFiles.java b/jni/testfixtures/app/opendocument/core/TestFiles.java
index 4ca12d5ad..b108c6cc8 100644
--- a/jni/testfixtures/app/opendocument/core/TestFiles.java
+++ b/jni/testfixtures/app/opendocument/core/TestFiles.java
@@ -8,6 +8,7 @@
 import java.nio.file.StandardCopyOption;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Locale;
 
 /**
  * The suite's input files.
@@ -86,7 +87,7 @@ static Path pdfFile(Path directory) throws IOException {
     int start = out.length();
     out.append("xref\n0 ").append(objects.size() + 1).append("\n0000000000 65535 f \n");
     for (int offset : offsets) {
-      out.append(String.format("%010d 00000 n \n", offset));
+      out.append(String.format(Locale.ROOT, "%010d 00000 n \n", offset));
     }
     out.append("trailer\n<< /Size ").append(objects.size() + 1).append(" /Root 1 0 R >>\n");
     out.append("startxref\n").append(start).append("\n%%EOF\n");