diff --git a/blockchain/client.go b/blockchain/client.go
index d4ad6a9..224bc7c 100644
--- a/blockchain/client.go
+++ b/blockchain/client.go
@@ -3,7 +3,6 @@ package blockchain
 import (
 	"context"
 	"fmt"
-	"math"
 	"sync"
 	"sync/atomic"
 
@@ -19,7 +18,7 @@ type EventsListener func(events *pallets.Events, blockNumber types.BlockNumber,
 type Client struct {
 	*gsrpc.SubstrateAPI
 
-	eventsListeners map[int]EventsListener
+	eventsListeners map[*EventsListener]struct{}
 	mu              sync.Mutex
 	isListening     uint32
 	cancelListening func()
@@ -43,7 +42,7 @@ func NewClient(url string) (*Client, error) {
 
 	return &Client{
 		SubstrateAPI:    substrateApi,
-		eventsListeners: make(map[int]EventsListener),
+		eventsListeners: make(map[*EventsListener]struct{}),
 		DdcClusters:     pallets.NewDdcClustersApi(substrateApi),
 		DdcCustomers:    pallets.NewDdcCustomersApi(substrateApi, meta),
 		DdcNodes:        pallets.NewDdcNodesApi(substrateApi, meta),
@@ -85,8 +84,8 @@ func (c *Client) StartEventsListening() (context.CancelFunc, <-chan error, error
 					set.Block,
 					func(events *pallets.Events, blockNumber types.BlockNumber, blockHash types.Hash) {
 						c.mu.Lock()
-						for _, callback := range c.eventsListeners {
-							go callback(events, blockNumber, blockHash)
+						for callback := range c.eventsListeners {
+							go (*callback)(events, blockNumber, blockHash)
 						}
 						c.mu.Unlock()
 					},
@@ -115,7 +114,8 @@ func (c *Client) RegisterEventsListener(begin types.BlockNumber, callback Events
 	pendingEvents := &pendingEvents{}
 	subscriptionStartBlock := uint32(0)
 	subscriptionStarted := make(chan struct{})
-	callbackWrapper := func(events *pallets.Events, blockNumber types.BlockNumber, blockHash types.Hash) {
+
+	callbackWrapper := EventsListener(func(events *pallets.Events, blockNumber types.BlockNumber, blockHash types.Hash) {
 		if atomic.CompareAndSwapUint32(&subscriptionStartBlock, 0, uint32(blockNumber)) {
 			close(subscriptionStarted)
 		}
@@ -125,21 +125,10 @@ func (c *Client) RegisterEventsListener(begin types.BlockNumber, callback Events
 		}
 
 		callback(events, blockNumber, blockHash)
-	}
+	})
 
 	c.mu.Lock()
-	// Find the smallest available key for the new listener.
-	var idx int
-	for i := 0; i <= math.MaxInt; i++ {
-		if _, ok := c.eventsListeners[i]; !ok {
-			idx = i
-			break
-		}
-		if i == math.MaxInt {
-			return nil, fmt.Errorf("too many events listeners")
-		}
-	}
-	c.eventsListeners[idx] = callbackWrapper
+	c.eventsListeners[&callbackWrapper] = struct{}{}
 	c.mu.Unlock()
 
 	cancelled := false
@@ -202,7 +191,7 @@ func (c *Client) RegisterEventsListener(begin types.BlockNumber, callback Events
 		once.Do(func() {
 			c.mu.Lock()
 			cancelled = true
-			delete(c.eventsListeners, idx)
+			delete(c.eventsListeners, &callbackWrapper)
 			c.mu.Unlock()
 		})
 	}