diff --git a/common/source/java/ch/systemsx/cisd/common/highwatermark/FileWithHighwaterMark.java b/common/source/java/ch/systemsx/cisd/common/highwatermark/FileWithHighwaterMark.java
index 92fe45ab73e62717566db15d8fe5fa17a95916b3..43d618498a3cd26e992bbebf2b24c8504c333638 100644
--- a/common/source/java/ch/systemsx/cisd/common/highwatermark/FileWithHighwaterMark.java
+++ b/common/source/java/ch/systemsx/cisd/common/highwatermark/FileWithHighwaterMark.java
@@ -35,6 +35,8 @@ import ch.systemsx.cisd.common.utilities.PropertyUtils;
 public final class FileWithHighwaterMark extends AbstractHashable implements Serializable
 {
 
+    static final String SEP = "-";
+
     public static final int DEFAULT_HIGHWATER_MARK = -1;
 
     private static final long serialVersionUID = 1L;
@@ -82,7 +84,7 @@ public final class FileWithHighwaterMark extends AbstractHashable implements Ser
         assert StringUtils.isNotBlank(filePropertyKey) : "File property key is blank";
         final String filePath = PropertyUtils.getMandatoryProperty(properties, filePropertyKey);
         final long highwaterMarkInKb =
-                PropertyUtils.getLong(properties, filePropertyKey.concat(".").concat(
+                PropertyUtils.getLong(properties, filePropertyKey.concat(SEP).concat(
                         HIGHWATER_MARK_PROPERTY_KEY), -1L);
         return new FileWithHighwaterMark(new File(filePath), highwaterMarkInKb);
     }
diff --git a/common/sourceTest/java/ch/systemsx/cisd/common/highwatermark/FileWithHighwaterMarkTest.java b/common/sourceTest/java/ch/systemsx/cisd/common/highwatermark/FileWithHighwaterMarkTest.java
index c72ce214cb061071fc5816d985c7e8d7ecb26c20..7c49ac89eb2ad55db3d7ef9c35f09c466a72e0d7 100644
--- a/common/sourceTest/java/ch/systemsx/cisd/common/highwatermark/FileWithHighwaterMarkTest.java
+++ b/common/sourceTest/java/ch/systemsx/cisd/common/highwatermark/FileWithHighwaterMarkTest.java
@@ -64,13 +64,13 @@ public final class FileWithHighwaterMarkTest
         assertEquals(new File(path), fileWithHighwaterMark.getFile());
         assertEquals(-1, fileWithHighwaterMark.getHighwaterMark());
         // 100Kb
-        properties.setProperty(filePropertyKey + "."
+        properties.setProperty(filePropertyKey + FileWithHighwaterMark.SEP
                 + FileWithHighwaterMark.HIGHWATER_MARK_PROPERTY_KEY, "100");
         fileWithHighwaterMark = FileWithHighwaterMark.fromProperties(properties, filePropertyKey);
         assertEquals(new File(path), fileWithHighwaterMark.getFile());
         assertEquals(100, fileWithHighwaterMark.getHighwaterMark());
         // Meaningless value
-        properties.setProperty(filePropertyKey + "."
+        properties.setProperty(filePropertyKey + FileWithHighwaterMark.SEP
                 + FileWithHighwaterMark.HIGHWATER_MARK_PROPERTY_KEY, "notANumber");
         fileWithHighwaterMark = FileWithHighwaterMark.fromProperties(properties, filePropertyKey);
         assertEquals(new File(path), fileWithHighwaterMark.getFile());