diff --git a/src/index.ts b/src/index.ts
index 197380db..77397989 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -2727,6 +2727,7 @@ export class GossipSub extends EventEmitter<GossipsubEvents> implements Initiali
   private onScrapeMetrics(metrics: Metrics): void {
     /* Data structure sizes */
     metrics.mcacheSize.set(this.mcache.size)
+    metrics.mcacheNotValidatedCount.set(this.mcache.notValidatedCount)
     // Arbitrary size
     metrics.cacheSize.set({ cache: 'direct' }, this.direct.size)
     metrics.cacheSize.set({ cache: 'seenCache' }, this.seenCache.size)
diff --git a/src/message-cache.ts b/src/message-cache.ts
index b33fc79e..6db09404 100644
--- a/src/message-cache.ts
+++ b/src/message-cache.ts
@@ -28,6 +28,9 @@ export class MessageCache {
 
   history: CacheEntry[][] = []
 
+  /** Track with accounting of messages in the mcache that are not yet validated */
+  notValidatedCount = 0
+
   /**
    * Holds history of messages in timebounded history arrays
    */
@@ -71,6 +74,10 @@ export class MessageCache {
 
     this.history[0].push({ ...messageId, topic: msg.topic })
 
+    if (!validated) {
+      this.notValidatedCount++
+    }
+
     return true
   }
 
@@ -143,6 +150,10 @@ export class MessageCache {
       return null
     }
 
+    if (!entry.validated) {
+      this.notValidatedCount--
+    }
+
     const { message, originatingPeers } = entry
     entry.validated = true
     // Clear the known peers list (after a message is validated, it is forwarded and we no
@@ -155,9 +166,15 @@ export class MessageCache {
    * Shifts the current window, discarding messages older than this.history.length of the cache
    */
   shift(): void {
-    const last = this.history[this.history.length - 1]
-    last.forEach((entry) => {
-      this.msgs.delete(entry.msgIdStr)
+    const lastCacheEntries = this.history[this.history.length - 1]
+    lastCacheEntries.forEach((cacheEntry) => {
+      const entry = this.msgs.get(cacheEntry.msgIdStr)
+      if (entry) {
+        this.msgs.delete(cacheEntry.msgIdStr)
+        if (!entry.validated) {
+          this.notValidatedCount--
+        }
+      }
     })
 
     this.history.pop()
diff --git a/src/metrics.ts b/src/metrics.ts
index 0d47f8ea..a09ebf1b 100644
--- a/src/metrics.ts
+++ b/src/metrics.ts
@@ -500,6 +500,10 @@ export function getMetrics(
       name: 'gossipsub_mcache_size',
       help: 'Current mcache msg count'
     }),
+    mcacheNotValidatedCount: register.gauge({
+      name: 'gossipsub_mcache_not_validated_count',
+      help: 'Current mcache msg count not validated'
+    }),
 
     topicStrToLabel: topicStrToLabel,