diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java
index b51a954ca..3a3e1c558 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/Repository.java
@@ -597,7 +597,7 @@ private ObjectId resolveSimple(final String revstr) throws IOException {
 			return resolveAbbreviation(revstr);
 
 		int dashg = revstr.indexOf("-g");
-		if (4 < revstr.length() && 0 <= dashg
+		if ((dashg + 4) < revstr.length() && 0 <= dashg
 				&& isHex(revstr.charAt(dashg + 2))
 				&& isHex(revstr.charAt(dashg + 3))
 				&& isAllHex(revstr, dashg + 4)) {