diff --git a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/CollectionCache.java b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/CollectionCache.java
index 90a385976..0901abab2 100644
--- a/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/CollectionCache.java
+++ b/network-store-iidm-impl/src/main/java/com/powsybl/network/store/iidm/impl/CollectionCache.java
@@ -120,6 +120,7 @@ public List<Resource<T>> getCachedResources() {
      */
     public void init() {
         fullyLoaded = true;
+        fullyLoadedExtensions = true;
     }
 
     public boolean isFullyLoaded() {
diff --git a/network-store-iidm-impl/src/test/java/com/powsybl/network/store/iidm/impl/CollectionCacheTest.java b/network-store-iidm-impl/src/test/java/com/powsybl/network/store/iidm/impl/CollectionCacheTest.java
index 499987a00..2b0734b01 100644
--- a/network-store-iidm-impl/src/test/java/com/powsybl/network/store/iidm/impl/CollectionCacheTest.java
+++ b/network-store-iidm-impl/src/test/java/com/powsybl/network/store/iidm/impl/CollectionCacheTest.java
@@ -334,6 +334,24 @@ public void removeResourceThenGetContainerTest() {
         assertEquals(1, collectionCache.getContainerResources(NETWORK_UUID, Resource.INITIAL_VARIANT_NUM, "vl1").size());
     }
 
+    @Test
+    public void initExtensionsTest() {
+        assertEquals(Arrays.asList(l1, l2, l3), collectionCache.getResources(NETWORK_UUID, Resource.INITIAL_VARIANT_NUM));
+        assertFalse(mockNetworkStoreClient.isExtensionAttributeLoaderCalled());
+        assertFalse(mockNetworkStoreClient.isExtensionAttributesLoaderByResourceTypeAndNameCalled());
+        assertFalse(mockNetworkStoreClient.isExtensionAttributesLoaderByIdCalled());
+        assertFalse(mockNetworkStoreClient.isExtensionAttributesLoaderByResourceTypeCalled());
+        collectionCache.init(); // it means we trust cache content and no more server loading
+        collectionCache.getExtensionAttributes(NETWORK_UUID, Resource.INITIAL_VARIANT_NUM, ResourceType.LOAD, "l1", "activePowerControl");
+        collectionCache.getAllExtensionsAttributesByResourceTypeAndExtensionName(NETWORK_UUID, Resource.INITIAL_VARIANT_NUM, ResourceType.LOAD, "activePowerControl");
+        collectionCache.getAllExtensionsAttributesByIdentifiableId(NETWORK_UUID, Resource.INITIAL_VARIANT_NUM, ResourceType.LOAD, "l1");
+        collectionCache.getAllExtensionsAttributesByResourceType(NETWORK_UUID, Resource.INITIAL_VARIANT_NUM, ResourceType.LOAD);
+        assertFalse(mockNetworkStoreClient.isExtensionAttributeLoaderCalled());
+        assertFalse(mockNetworkStoreClient.isExtensionAttributesLoaderByResourceTypeAndNameCalled());
+        assertFalse(mockNetworkStoreClient.isExtensionAttributesLoaderByIdCalled());
+        assertFalse(mockNetworkStoreClient.isExtensionAttributesLoaderByResourceTypeCalled());
+    }
+
     @Test
     public void getExtensionAttributesWithResourceNotCachedMustThrow() {
         PowsyblException exception = assertThrows(PowsyblException.class, () -> collectionCache.getExtensionAttributes(NETWORK_UUID, Resource.INITIAL_VARIANT_NUM, ResourceType.LOAD, "l1", "activePowerControl"));