Index: core/src/main/java/org/springframework/osgi/service/importer/support/ServiceReferenceDelegate.java
===================================================================
--- core/src/main/java/org/springframework/osgi/service/importer/support/ServiceReferenceDelegate.java	(revision 13141)
+++ core/src/main/java/org/springframework/osgi/service/importer/support/ServiceReferenceDelegate.java	(working copy)
@@ -58,4 +58,9 @@
 	public String toString() {
 		return "ServiceReference wrapper for " + delegate.getServiceReference();
 	}
+
+    public int compareTo(Object reference) {
+        return this.delegate.getServiceReference().compareTo(
+            (((ServiceReferenceDelegate) reference).delegate.getServiceReference()));
+    }
 }
Index: core/src/main/java/org/springframework/osgi/service/importer/support/internal/aop/SwappingServiceReferenceProxy.java
===================================================================
--- core/src/main/java/org/springframework/osgi/service/importer/support/internal/aop/SwappingServiceReferenceProxy.java	(revision 13141)
+++ core/src/main/java/org/springframework/osgi/service/importer/support/internal/aop/SwappingServiceReferenceProxy.java	(working copy)
@@ -80,4 +80,8 @@
 	public int hashCode() {
 		return HASH_CODE + delegate.hashCode();
 	}
+
+    public int compareTo(Object reference) {
+        return this.delegate.compareTo(((SwappingServiceReferenceProxy) reference).delegate);
+    }
 }
Index: core/src/main/java/org/springframework/osgi/service/importer/support/internal/aop/StaticServiceReferenceProxy.java
===================================================================
--- core/src/main/java/org/springframework/osgi/service/importer/support/internal/aop/StaticServiceReferenceProxy.java	(revision 13141)
+++ core/src/main/java/org/springframework/osgi/service/importer/support/internal/aop/StaticServiceReferenceProxy.java	(working copy)
@@ -81,4 +81,8 @@
 	public int hashCode() {
 		return HASH_CODE + target.hashCode();
 	}
+
+    public int compareTo(Object reference) {
+        return this.target.compareTo(((StaticServiceReferenceProxy) reference).target);
+    }
 }
Index: mock/src/main/java/org/springframework/osgi/mock/MockServiceReference.java
===================================================================
--- mock/src/main/java/org/springframework/osgi/mock/MockServiceReference.java	(revision 13141)
+++ mock/src/main/java/org/springframework/osgi/mock/MockServiceReference.java	(working copy)
@@ -203,4 +203,35 @@
 		return "mock service reference [owning bundle id=" + bundle.hashCode() + "|props : " + properties + "]";
 	}
 
+    public int compareTo(Object reference) {
+        ServiceReference other = (ServiceReference)reference;
+        
+        Integer thisRankingInteger = (Integer)this.properties.get(Constants.SERVICE_RANKING);
+        int thisRanking = (thisRankingInteger instanceof Integer)?((Integer)thisRankingInteger).intValue() : 0;
+
+        Integer otherRankingInteger = (Integer)other.getProperty(Constants.SERVICE_RANKING);
+        int otherRanking = (otherRankingInteger instanceof Integer)?((Integer)otherRankingInteger).intValue() : 0;
+        
+        int result = otherRanking - thisRanking;
+        if(result == 0) {
+            Long thisIdLong = (Long)this.properties.get(Constants.SERVICE_RANKING);
+            long thisId = (thisIdLong instanceof Long)?((Long)thisIdLong).longValue() : 0;
+
+            Long otherIdLong = (Long)other.getProperty(Constants.SERVICE_RANKING);
+            long otherId = (otherIdLong instanceof Long)?((Long)otherIdLong).longValue() : 0;
+
+            if(thisId < otherId) {
+                result = -1;
+            }
+            else if(otherId < thisId) {
+                result = 1;
+            }
+            else {
+                result = 0;
+            }
+        }
+
+        return result;
+    }
+
 }