diff --git a/include/coap2/resource.h b/include/coap2/resource.h
index c7239b13..b81dbb91 100644
--- a/include/coap2/resource.h
+++ b/include/coap2/resource.h
@@ -419,7 +419,8 @@ coap_resource_t *coap_get_resource_from_uri_path(coap_context_t *context,
  * @param session         The observer's session
  * @param token           The token that identifies this subscription.
  * @param query           The query string, if any. subscription will
-                          take ownership of the string.
+ *                        take ownership of the string unless this
+ *                        function returns NULL.
  * @param has_block2      If Option Block2 defined.
  * @param block2          Contents of Block2 if Block 2 defined.
  * @return                A pointer to the added/updated subscription
diff --git a/src/net.c b/src/net.c
index e4e977a2..035ae836 100644
--- a/src/net.c
+++ b/src/net.c
@@ -2278,8 +2278,11 @@ handle_request(coap_context_t *context, coap_session_t *session, coap_pdu_t *pdu
               has_block2 = 1;
             }
             subscription = coap_add_observer(resource, session, &token, query, has_block2, block2);
-            owns_query = 0;
             if (subscription) {
+              /* Ownership of query is taken by subscription if not
+               * NULL. In this case, we must not delete query here
+               * hence owns_query is cleared. */
+              owns_query = 0;
               coap_touch_observer(context, session, &token);
             }
           }
diff --git a/src/resource.c b/src/resource.c
index 5eda13dc..4a5b7a76 100644
--- a/src/resource.c
+++ b/src/resource.c
@@ -674,8 +674,9 @@ coap_add_observer(coap_resource_t *resource,
   s = COAP_MALLOC_TYPE(subscription);
 
   if (!s) {
-    if (query)
-      coap_delete_string(query);
+    /* query is not deleted so it can be used in the calling function
+     * which must give up ownership of query only if this function
+     * does not return NULL. */
     return NULL;
   }