diff --git a/core/api/src/main/java/org/onosproject/net/provider/AbstractProviderRegistry.java b/core/api/src/main/java/org/onosproject/net/provider/AbstractProviderRegistry.java
index 2c89221..bfd54bf 100644
--- a/core/api/src/main/java/org/onosproject/net/provider/AbstractProviderRegistry.java
+++ b/core/api/src/main/java/org/onosproject/net/provider/AbstractProviderRegistry.java
@@ -17,6 +17,8 @@
 
 import com.google.common.collect.ImmutableSet;
 import org.onosproject.net.DeviceId;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.HashMap;
 import java.util.Map;
@@ -55,24 +57,37 @@
         return null;
     }
 
+    private static final Logger log = LoggerFactory
+        .getLogger(AbstractProviderRegistry.class);
+
     @Override
     public synchronized S register(P provider) {
+
+        log.debug("registering provider {} :{}", provider, provider.id());
         checkNotNull(provider, "Provider cannot be null");
-        checkState(!services.containsKey(provider.id()), "Provider %s already registered", provider.id());
 
         // If the provider is a primary one, check for a conflict.
         ProviderId pid = provider.id();
         checkState(pid.isAncillary() || !providersByScheme.containsKey(pid.scheme()),
-                   "A primary provider with id %s is already registered",
-                   providersByScheme.get(pid.scheme()));
+            "A primary provider with id %s is already registered",
+            providersByScheme.get(pid.scheme()));
 
-        S service = createProviderService(provider);
-        services.put(provider.id(), service);
-        providers.put(provider.id(), provider);
+        checkState(pid.isAncillary() || !services.containsKey(provider.id()),
+            "Provider %s already registered", provider.id());
 
         // Register the provider by URI scheme only if it is not ancillary.
+        S service = null;
+
         if (!pid.isAncillary()) {
+            service = createProviderService(provider);
+            services.put(provider.id(), service);
+            providers.put(provider.id(), provider);
             providersByScheme.put(pid.scheme(), provider);
+        } else {
+            ProviderId servicePid = new ProviderId(provider.id().scheme(), provider.id().id(), false);
+            service = services.get(servicePid);
+            checkState(service != null,
+                "Primary provider with id %s not registered yet", pid);
         }
 
         return service;