The invention is concerned with insertion of secondary content in a time slot of primary content. The primary content and the secondary content are provided to a receiver via a managed content delivery network configured for IPTV delivery. The secondary content may be personalized content, such as an ad. Both the primary content and the secondary content may be encrypted, and decryptable with different decryption keys. Measures are described for pre-caching the decryption key for the secondary content at the receiver ahead of a scheduled play-out time of the secondary content. By pre-caching the decryption key, an interruption in play-out may be avoided or reduced compared to a basic scenario in which the receiver requests the decryption key at or immediately before the scheduled play-out time.