The Samaritan Pentecost

When Philip preached in Samaria the people listened, believed the Gospel and were baptized (Acts 8:5-7, 12). However, Luke tells us that, when Peter and John learned of the Samaritan’s repentance and came to the Samaritan village where Philip was preaching (Acts 8:14), they found the new believers had not received the Holy Spirit (Acts 8:16)! Why would this be so? Was anything lacking in Philip’s preaching?