diff --git a/src/server.c b/src/server.c
index 0728707d3..f1ba5555c 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1055,7 +1055,16 @@ void removeClientFromMemUsageBucket(client *c, int allow_eviction) {
  * returns 1 if client eviction for this client is allowed, 0 otherwise.
  */
 int updateClientMemUsageAndBucket(client *c) {
-    serverAssert(pthread_equal(pthread_self(), server.main_thread_id) && c->conn);
+    /* The unlikely case this function was called from a thread different
+     * than the main one is a module call from a spawned thread. This is safe
+     * since this call must have been made after calling
+     * RedisModule_ThreadSafeContextLock i.e the module is holding the GIL. In
+     * that special case we assert that at least the updated client's
+     * running_tid is the main thread. The true main thread is allowed to call
+     * this function on clients handled by IO-threads as it makes sure the
+     * IO-threads are paused, f.e see cleintsCron() and evictClients(). */
+    serverAssert((pthread_equal(pthread_self(), server.main_thread_id) ||
+                  c->running_tid == IOTHREAD_MAIN_THREAD_ID) && c->conn);
     int allow_eviction = clientEvictionAllowed(c);
     removeClientFromMemUsageBucket(c, allow_eviction);
 
diff --git a/tests/unit/moduleapi/usercall.tcl b/tests/unit/moduleapi/usercall.tcl
index 0f7a318f7..05f333180 100644
--- a/tests/unit/moduleapi/usercall.tcl
+++ b/tests/unit/moduleapi/usercall.tcl
@@ -134,6 +134,24 @@ start_server {tags {"modules usercall"}} {
         assert_match {*cmd=usercall.call_with_user_flag*} [dict get $entry client-info]
     }
 
+    test {server not crashing when MONITOR is fed from spawned thread} {
+        set rd [redis_deferring_client]
+        $rd monitor
+
+        r ACL LOG RESET
+        assert_equal [r usercall.reset_user] OK
+        assert_equal [r usercall.add_to_acl "~* &* +@all -set"] OK
+
+        r flushdb
+        r set x x
+
+        # This is enough. This checks that we don't crash inside
+        # updateClientMemUsageAndBucket
+        assert_equal x [r usercall.call_with_user_bg C get x]
+
+        $rd close
+    }
+
     start_server {tags {"wait aof network external:skip"}} {
         set slave [srv 0 client]
         set slave_host [srv 0 host]