diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/diff/SimilarityIndex.java b/org.eclipse.jgit/src/org/eclipse/jgit/diff/SimilarityIndex.java
index d6026b5be..f4cccfc37 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/diff/SimilarityIndex.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/diff/SimilarityIndex.java
@@ -144,6 +144,8 @@ class SimilarityIndex {
 
 	int score(SimilarityIndex dst) {
 		long max = Math.max(fileSize, dst.fileSize);
+		if (max == 0)
+			return 100;
 		return (int) ((common(dst) * 100L) / max);
 	}