diff --git a/src/main/java/com/darichey/discord/CommandListener.java b/src/main/java/com/darichey/discord/CommandListener.java
index 2dc9c7c..f164d03 100644
--- a/src/main/java/com/darichey/discord/CommandListener.java
+++ b/src/main/java/com/darichey/discord/CommandListener.java
@@ -18,7 +18,7 @@ public CommandListener(CommandRegistry registry) {
 	@Override
 	public void handle(MessageReceivedEvent event) {
 		String content = event.getMessage().getContent();
-		String prefix = registry.getEffectivePrefix(event.getGuild().getLongID());
+		String prefix = registry.getEffectivePrefix(event.getGuild());
 
 		if (content.startsWith(prefix)) {
 			String prefixRemoved = content.substring(prefix.length());
diff --git a/src/main/java/com/darichey/discord/CommandRegistry.java b/src/main/java/com/darichey/discord/CommandRegistry.java
index 5e85a13..732779d 100644
--- a/src/main/java/com/darichey/discord/CommandRegistry.java
+++ b/src/main/java/com/darichey/discord/CommandRegistry.java
@@ -125,16 +125,17 @@ public Optional<String> getPrefixForGuild(long id) {
 	/**
 	 * Gets the prefix for the given guild. This is either the guild-specific prefix or the default prefix if one is not set.
 	 * @param guild The guild to look up.
-	 * @return The guild-specific prefix for this guild or
+	 * @return The guild-specific prefix for this guild or the default prefix.
 	 */
 	public String getEffectivePrefix(IGuild guild) {
-		return getEffectivePrefix(guild.getLongID());
+		if (guild == null) return defaultPrefix;
+		else return getEffectivePrefix(guild.getLongID());
 	}
 
 	/**
 	 * Gets the prefix for the given guild. This is either the guild-specific prefix or the default prefix if one is not set.
 	 * @param id The id of the guild to look up.
-	 * @return The guild-specific prefix for this guild or
+	 * @return The guild-specific prefix for this guild or the default prefix.
 	 */
 	public String getEffectivePrefix(long id) {
 		return getPrefixForGuild(id).orElse(defaultPrefix);