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 13136)
+++ 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 13136)
+++ 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 13136)
+++ 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);
+    }
 }