diff --git a/src/java/org/apache/lucene/document/DateField.java b/src/java/org/apache/lucene/document/DateField.java
index b555490fb6c..f917cfe354f 100644
--- a/src/java/org/apache/lucene/document/DateField.java
+++ b/src/java/org/apache/lucene/document/DateField.java
@@ -109,7 +109,7 @@ public class DateField {
     if (s.length() < DATE_LEN) {
       StringBuffer sb = new StringBuffer(s);
       while (sb.length() < DATE_LEN)
-        sb.insert(0, ' ');
+        sb.insert(0, 0);
       s = sb.toString();
     }