Chatbots have attracted considerable interest in recent years. A key design challenge to increase their adoption is to make the interaction with them feel natural and human-like. Therefore, it is suggested to incorporate social cues in the chatbot design. Drawing on the Computers are Social Actors paradigm and the "uncanny valley" hypothesis, we study the effect of one specific social cue (i.e., typing indicators) on social presence of chatbots. In an online experiment, we investigate the effect of two specific designs of typing indicators. Our preliminary results indicate that graphical typing indicators increase social presence of chatbots, but only for novice users. Therefore, our results suggest that the relationship between typing indicators and perceived social presence of chatbots depends on the design of these indicators and user's prior experience. We contribute with empirical insights and design knowledge that support researchers and practitioners in understanding and designing more natural human-chatbot interactions.