diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/GitDateParser.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/GitDateParser.java
index a339b9a..56a1731 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/GitDateParser.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/GitDateParser.java
@@ -126,7 +126,7 @@ enum ParseableSimpleDateFormat {
 		DEFAULT("EEE MMM dd HH:mm:ss yyyy Z"), // //$NON-NLS-1$
 		LOCAL("EEE MMM dd HH:mm:ss yyyy"); //$NON-NLS-1$
 
-		String formatStr;
+		private final String formatStr;
 
 		private ParseableSimpleDateFormat(String formatStr) {
 			this.formatStr = formatStr;