diff --git a/src/fr/inrialpes/exmo/align/impl/BasicAlignment.java b/src/fr/inrialpes/exmo/align/impl/BasicAlignment.java
index 0a12197500d714a739b2695205f392dff0385dba..7c2ec0f12e8f39a6182d5f4c911ee857341ea25d 100644
--- a/src/fr/inrialpes/exmo/align/impl/BasicAlignment.java
+++ b/src/fr/inrialpes/exmo/align/impl/BasicAlignment.java
@@ -506,6 +506,7 @@ public class BasicAlignment implements Alignment {
 	    String label = (String)e.nextElement();
 	    result.setExtension( label, getExtension( label ) );
 	}
+	result.setExtension( "id", (String)null );
 	for ( Enumeration e = getElements() ; e.hasMoreElements(); ){
 	    result.addCell(((Cell)e.nextElement()).inverse());
 	}
@@ -531,10 +532,10 @@ public class BasicAlignment implements Alignment {
 
     /**
      * Generate a copy of this alignment object
+     * It has the same content but a different id (no id indeed)
      */
     public Object clone() {
 	BasicAlignment align = new BasicAlignment();
-	//*/align.init( (OWLOntology)getOntology1(), (OWLOntology)getOntology2() );
 	try {
 	    align.init( getOntology1(), getOntology2() );
 	    // This method is never launched by the present class
@@ -547,9 +548,9 @@ public class BasicAlignment implements Alignment {
 	    String label = (String)e.nextElement();
 	    align.setExtension( label, getExtension( label ) );
 	}
-	try {
-	    align.ingest( this );
-	} catch (AlignmentException ex) { ex.printStackTrace(); }
+	align.getExtensions().unsetParameter( "id" );
+	try { align.ingest( this ); }
+	catch (AlignmentException ex) { ex.printStackTrace(); }
 	return align;
     }
 
diff --git a/src/fr/inrialpes/exmo/align/impl/OWLAPIAlignment.java b/src/fr/inrialpes/exmo/align/impl/OWLAPIAlignment.java
index e273c966b794a1f8df2859e259b1d8d3b46e6067..05aa5a5d90a1971c404efd25a5ac2db3fe82f0af 100644
--- a/src/fr/inrialpes/exmo/align/impl/OWLAPIAlignment.java
+++ b/src/fr/inrialpes/exmo/align/impl/OWLAPIAlignment.java
@@ -221,6 +221,7 @@ public class OWLAPIAlignment extends BasicAlignment {
 	    String label = (String)e.nextElement();
 	    align.setExtension( label, getExtension( label ) );
 	}
+	align.getExtensions().unsetParameter( "id" );
 	try {
 	    align.ingest( this );
 	} catch (AlignmentException ex) { ex.printStackTrace(); }
diff --git a/src/fr/inrialpes/exmo/align/impl/URIAlignment.java b/src/fr/inrialpes/exmo/align/impl/URIAlignment.java
index 59fe07c22d9fc3ced1bd1a0b8b9600215798062a..a95407e6b430fed789f5cc536e170c12a9b1f6fb 100644
--- a/src/fr/inrialpes/exmo/align/impl/URIAlignment.java
+++ b/src/fr/inrialpes/exmo/align/impl/URIAlignment.java
@@ -173,6 +173,7 @@ public class URIAlignment extends BasicAlignment {
 	    String label = (String)e.nextElement();
 	    align.setExtension( label, getExtension( label ) );
 	}
+	align.getExtensions().unsetParameter( "id" );
 	try {
 	    align.ingest( this );
 	} catch (AlignmentException ex) { ex.printStackTrace(); }