diff --git a/src/main/java/dev/logal/logalbot/audio/TrackScheduler.java b/src/main/java/dev/logal/logalbot/audio/TrackScheduler.java
index da39ef4..34510c6 100644
--- a/src/main/java/dev/logal/logalbot/audio/TrackScheduler.java
+++ b/src/main/java/dev/logal/logalbot/audio/TrackScheduler.java
@@ -80,7 +80,7 @@ public final class TrackScheduler extends AudioEventAdapter {
     }
 
     public final void removeFromQueue(final int index) {
-        Checks.notNull(index, "Index");
+        Checks.positive(index, "Index");
 
         logger.info("Track '" + queue.remove(index).getTrack().getInfo().title + "' has been removed from the queue in "
                 + this.guild.getName() + " (" + this.guild.getId() + ").");
@@ -110,8 +110,6 @@ public final class TrackScheduler extends AudioEventAdapter {
     }
 
     public final void setQueueLocked(final boolean locked) {
-        Checks.notNull(locked, "Locked");
-
         this.queueLocked = locked;
     }
 
@@ -124,6 +122,8 @@ public final class TrackScheduler extends AudioEventAdapter {
     }
 
     public final int occupiedSlotCount(Member member) {
+        Checks.notNull(member, "Member");
+
         int count = 0;
         for (RequestedTrack requestedTrack : this.queue) {
             if (requestedTrack.getRequester().equals(member)) {
diff --git a/src/main/java/dev/logal/logalbot/commands/CommandResponse.java b/src/main/java/dev/logal/logalbot/commands/CommandResponse.java
index 37d867a..e9e82d2 100644
--- a/src/main/java/dev/logal/logalbot/commands/CommandResponse.java
+++ b/src/main/java/dev/logal/logalbot/commands/CommandResponse.java
@@ -44,8 +44,8 @@ public final class CommandResponse {
     private TimeUnit deletionDelayUnit, expireDelayUnit;
 
     public CommandResponse(final String emoji, final String response) {
-        Checks.notNull(emoji, "Emoji");
-        Checks.notNull(response, "Response");
+        Checks.notEmpty(emoji, "Emoji");
+        Checks.notEmpty(response, "Response");
 
         this.emoji = EmojiManager.getForAlias(emoji);
         this.response = response;
@@ -59,7 +59,7 @@ public final class CommandResponse {
     }
 
     public final CommandResponse setDeletionDelay(final long delay, final TimeUnit unit) {
-        Checks.notNull(delay, "Delay");
+        Checks.positive(delay, "Delay");
         Checks.notNull(unit, "Unit");
 
         this.deletionDelay = delay;
@@ -68,7 +68,7 @@ public final class CommandResponse {
     }
 
     public final CommandResponse addReactionCallback(final String emoji, final ReactionCallback callback) {
-        Checks.notNull(emoji, "Emoji");
+        Checks.notEmpty(emoji, "Emoji");
         Checks.notNull(callback, "Callback");
 
         this.callbacks.put(EmojiManager.getForAlias(emoji), callback);
@@ -83,7 +83,7 @@ public final class CommandResponse {
     }
 
     public final CommandResponse setReactionCallbackExpireDelay(final long delay, final TimeUnit unit) {
-        Checks.notNull(delay, "Delay");
+        Checks.positive(delay, "Delay");
         Checks.notNull(unit, "Unit");
 
         this.expireDelay = delay;
diff --git a/src/main/java/dev/logal/logalbot/utils/AudioUtil.java b/src/main/java/dev/logal/logalbot/utils/AudioUtil.java
index 1350c4d..7cc1cc7 100644
--- a/src/main/java/dev/logal/logalbot/utils/AudioUtil.java
+++ b/src/main/java/dev/logal/logalbot/utils/AudioUtil.java
@@ -132,7 +132,6 @@ public final class AudioUtil {
 
     public static final void setPausedState(final Guild guild, final boolean pausedState) {
         Checks.notNull(guild, "Guild");
-        Checks.notNull(pausedState, "Paused state");
 
         guild.getAudioManager().setSelfMuted(pausedState);
         players.get(guild.getIdLong()).setPaused(pausedState);
@@ -166,7 +165,7 @@ public final class AudioUtil {
     }
 
     public static final void findTrack(final String query, final Member requester, final TextChannel channel) {
-        Checks.notNull(query, "Query");
+        Checks.notEmpty(query, "Query");
         Checks.notNull(requester, "Requester");
         Checks.notNull(channel, "Channel");
 
diff --git a/src/main/java/dev/logal/logalbot/utils/ReactionCallbackManager.java b/src/main/java/dev/logal/logalbot/utils/ReactionCallbackManager.java
index a581144..fb06b5e 100644
--- a/src/main/java/dev/logal/logalbot/utils/ReactionCallbackManager.java
+++ b/src/main/java/dev/logal/logalbot/utils/ReactionCallbackManager.java
@@ -72,7 +72,8 @@ public final class ReactionCallbackManager {
 
     public static final void executeCallback(final long messageID, final TextChannel channel, final Member reactor,
             final String emoji) {
-        Checks.notNull(messageID, "Message ID");
+        Checks.positive(messageID, "Message ID");
+        Checks.notNull(channel, "Channel");
         Checks.notNull(reactor, "Reactor");
         Checks.notEmpty(emoji, "Emoji");
 
diff --git a/src/main/java/dev/logal/logalbot/utils/Scheduler.java b/src/main/java/dev/logal/logalbot/utils/Scheduler.java
index 3b7c146..b487f11 100644
--- a/src/main/java/dev/logal/logalbot/utils/Scheduler.java
+++ b/src/main/java/dev/logal/logalbot/utils/Scheduler.java
@@ -30,7 +30,7 @@ public final class Scheduler {
 
     public static final ScheduledFuture<?> schedule(final Runnable runnable, final long delay, final TimeUnit unit) {
         Checks.notNull(runnable, "Runnable");
-        Checks.notNull(delay, "Delay");
+        Checks.positive(delay, "Delay");
         Checks.notNull(unit, "Unit");
 
         return pool.schedule(runnable, delay, unit);
@@ -39,8 +39,8 @@ public final class Scheduler {
     public static final ScheduledFuture<?> scheduleRepeating(final Runnable runnable, final long initialDelay,
             final long period, final TimeUnit unit) {
         Checks.notNull(runnable, "Runnable");
-        Checks.notNull(initialDelay, "Initial delay");
-        Checks.notNull(period, "Period");
+        Checks.positive(initialDelay, "Initial delay");
+        Checks.positive(period, "Period");
         Checks.notNull(unit, "Unit");
 
         return pool.scheduleAtFixedRate(runnable, initialDelay, period, unit);
diff --git a/src/main/java/dev/logal/logalbot/utils/StringUtil.java b/src/main/java/dev/logal/logalbot/utils/StringUtil.java
index 1236edd..dfd2bf0 100644
--- a/src/main/java/dev/logal/logalbot/utils/StringUtil.java
+++ b/src/main/java/dev/logal/logalbot/utils/StringUtil.java
@@ -81,7 +81,7 @@ public final class StringUtil {
     }
 
     public static final String formatTime(final long milliseconds) {
-        Checks.notNull(milliseconds, "Milliseconds");
+        Checks.positive(milliseconds, "Milliseconds");
 
         final long second = (milliseconds / 1000) % 60;
         final long minute = (milliseconds / (1000 * 60)) % 60;
diff --git a/src/main/java/dev/logal/logalbot/utils/TrackUtil.java b/src/main/java/dev/logal/logalbot/utils/TrackUtil.java
index 57a4a49..521261a 100644
--- a/src/main/java/dev/logal/logalbot/utils/TrackUtil.java
+++ b/src/main/java/dev/logal/logalbot/utils/TrackUtil.java
@@ -65,7 +65,6 @@ public final class TrackUtil {
 
     public static final MessageEmbed trackListInfoEmbed(final List<RequestedTrack> tracks, final boolean numbered) {
         Checks.notNull(tracks, "Tracks");
-        Checks.notNull(numbered, "Numbered");
 
         final EmbedBuilder builder = new EmbedBuilder();
         for (int i = 0; i < tracks.size(); i++) {
@@ -94,7 +93,6 @@ public final class TrackUtil {
 
     public static final MessageEmbed pagedTrackListInfoEmbed(final List<RequestedTrack> tracks, int page) {
         Checks.notNull(tracks, "Tracks");
-        Checks.notNull(page, "Page");
 
         final EmbedBuilder builder = new EmbedBuilder();
         if (page < 1) {
@@ -124,7 +122,6 @@ public final class TrackUtil {
 
     public static final boolean doesGreaterPageExist(final List<RequestedTrack> tracks, int page) {
         Checks.notNull(tracks, "Tracks");
-        Checks.notNull(page, "Page");
 
         final int pages = (int) Math.ceil(tracks.size() / 10d);
         return (page < pages);