diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java
index 3d700ac49..a9522452b 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/ObjectInserter.java
@@ -378,12 +378,15 @@ public abstract class ObjectInserter {
 			w.write(tag.getTag());
 			w.write("\n");
 
-			w.write("tagger ");
-			w.write(tag.getTagger().toExternalString());
-			w.write('\n');
+			if (tag.getTagger() != null) {
+				w.write("tagger ");
+				w.write(tag.getTagger().toExternalString());
+				w.write('\n');
+			}
 
 			w.write('\n');
-			w.write(tag.getMessage());
+			if (tag.getMessage() != null)
+				w.write(tag.getMessage());
 			w.close();
 		} catch (IOException err) {
 			// This should never occur, the only way to get it above is