diff --git a/common/source/java/ch/systemsx/cisd/common/utilities/FileUtilities.java b/common/source/java/ch/systemsx/cisd/common/utilities/FileUtilities.java
index a4fd2b8c61c35e661bb3886e60a49c931d06a3fc..8c41ad8126e58baddbb51f55707dc640e975142e 100644
--- a/common/source/java/ch/systemsx/cisd/common/utilities/FileUtilities.java
+++ b/common/source/java/ch/systemsx/cisd/common/utilities/FileUtilities.java
@@ -478,7 +478,7 @@ public final class FileUtilities
      * @param defaultFileName the default name for the new file if the digit pattern could not be found (probably the
      *            starting file).
      * @param regex pattern to find out the counter. If <code>null</code> then {@link #ONE_OR_MORE_DIGITS}} will be
-     *            taken. The given <var>regex</var> must contain <code>(\\d+)</code>.
+     *            taken. The given <var>regex</var> must contain <code>(\\d+)</code> or <code>([0-9]+)</code>.
      */
     public final static File createNextNumberedFile(File path, Pattern regex, String defaultFileName)
     {
@@ -491,7 +491,7 @@ public final class FileUtilities
         {
             pattern = regex;
         }
-        assert pattern.pattern().indexOf("(\\d+)") > -1;
+        assert pattern.pattern().indexOf("(\\d+)") > -1 || pattern.pattern().indexOf("([0-9]+)") > -1;
 
         String pathName = path.getName();
         final Matcher matcher = pattern.matcher(pathName);
diff --git a/common/sourceTest/java/ch/systemsx/cisd/common/utilities/FileUtilitiesTest.java b/common/sourceTest/java/ch/systemsx/cisd/common/utilities/FileUtilitiesTest.java
index 56f446b9ab45f9ebed1f9fe5f0c52b6460e7d21e..57c82262047b5b77b5c3dec1fa3505ff9b69e032 100644
--- a/common/sourceTest/java/ch/systemsx/cisd/common/utilities/FileUtilitiesTest.java
+++ b/common/sourceTest/java/ch/systemsx/cisd/common/utilities/FileUtilitiesTest.java
@@ -190,6 +190,14 @@ public class FileUtilitiesTest
         {
             // Nothing to do here
         }
+        try
+        {
+            FileUtilities.createNextNumberedFile(file, Pattern.compile("dummyPattern"), "abc_[1]");
+            fail("Must contain either '(\\d+)' or ([0-9]+).");
+        } catch (AssertionError e)
+        {
+            // Nothing to do here
+        }
         newFile = FileUtilities.createNextNumberedFile(file, pattern, "abc_[1]");
         assertEquals(FilenameUtils.getName(new File(workingDirectory, "abc_[1]").getPath()), FilenameUtils
                 .getName(newFile.getPath()));