diff --git a/jar/signatures-1.0-SNAPSHOT.jar b/jar/signatures-1.0-SNAPSHOT.jar
index 8b23e7bed27..d0a2fb3c3f8 100644
Binary files a/jar/signatures-1.0-SNAPSHOT.jar and b/jar/signatures-1.0-SNAPSHOT.jar differ
diff --git a/src/main/org/openscience/cdk/signature/AtomSignature.java b/src/main/org/openscience/cdk/signature/AtomSignature.java
index fee5290dc73..eed84f3d2c5 100644
--- a/src/main/org/openscience/cdk/signature/AtomSignature.java
+++ b/src/main/org/openscience/cdk/signature/AtomSignature.java
@@ -71,6 +71,16 @@ public AtomSignature(int atomIndex, int height, IAtomContainer molecule) {
         this.molecule = molecule;
         super.create(atomIndex, molecule.getAtomCount(), height);
     }
+    
+    public AtomSignature(int atomIndex, int height, 
+            InvariantType invariantType, IAtomContainer molecule) {
+        super(invariantType);
+    }
+    
+    public int getIntLabel(int vertexIndex) {
+        IAtom atom = molecule.getAtom(vertexIndex);
+        return atom.getMassNumber();
+    }
 
     /* (non-Javadoc)
      * @see signature.AbstractVertexSignature#getConnected(int)
diff --git a/src/test/org/openscience/cdk/signature/AtomSignatureTest.java b/src/test/org/openscience/cdk/signature/AtomSignatureTest.java
index 2befbbd40ef..7b7c412b863 100644
--- a/src/test/org/openscience/cdk/signature/AtomSignatureTest.java
+++ b/src/test/org/openscience/cdk/signature/AtomSignatureTest.java
@@ -39,6 +39,30 @@
  */
 public class AtomSignatureTest extends AbstractSignatureTest {
     
+    @Test
+    public void integerInvariantsTest() {
+        IMolecule isotopeChiralMol = builder.newInstance(IMolecule.class);
+        isotopeChiralMol.addAtom(builder.newInstance(IAtom.class, "C"));
+        
+        IAtom s32 = builder.newInstance(IAtom.class, "S");
+        s32.setMassNumber(32);
+        isotopeChiralMol.addAtom(s32);
+        
+        IAtom s33 = builder.newInstance(IAtom.class, "S");
+        s33.setMassNumber(33);
+        isotopeChiralMol.addAtom(s33);
+        
+        IAtom s34 = builder.newInstance(IAtom.class, "S");
+        s34.setMassNumber(34);
+        isotopeChiralMol.addAtom(s34);
+        
+        IAtom s36 = builder.newInstance(IAtom.class, "S");
+        s36.setMassNumber(36);
+        isotopeChiralMol.addAtom(s36);
+        
+        
+    }
+    
     @Test
     public void heightTest() {
         IMolecule benzene = makeBenzene();