diff --git a/src/main/java/com/mojang/brigadier/CommandDispatcher.java b/src/main/java/com/mojang/brigadier/CommandDispatcher.java
index 2d28761..4d69fe2 100644
--- a/src/main/java/com/mojang/brigadier/CommandDispatcher.java
+++ b/src/main/java/com/mojang/brigadier/CommandDispatcher.java
@@ -23,6 +23,12 @@ import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.FutureTask;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
 
@@ -285,11 +291,8 @@ public class CommandDispatcher<S> {
         return self;
     }
 
-    public CommandSuggestions getCompletionSuggestions(final ParseResults<S> parse) {
+    public CompletableFuture<CommandSuggestions> getCompletionSuggestions(final ParseResults<S> parse) {
         final CommandContextBuilder<S> context = parse.getContext();
-
-        final Set<String> suggestions = new LinkedHashSet<>();
-
         final CommandNode<S> parent;
         final int start;
 
@@ -309,13 +312,24 @@ public class CommandDispatcher<S> {
             start = 0;
         }
 
+        @SuppressWarnings("unchecked") final CompletableFuture<Collection<String>>[] futures = new CompletableFuture[parent.getChildren().size()];
+        int i = 0;
         for (final CommandNode<S> node : parent.getChildren()) {
-            node.listSuggestions(parse.getReader().getString().substring(start), suggestions, context);
+            futures[i++] = node.listSuggestions(parse.getReader().getString().substring(start));
         }
 
-        final List<String> result = new ArrayList<>(suggestions);
-        Collections.sort(result);
-        return new CommandSuggestions(new StringRange(start, parse.getReader().getTotalLength()), result);
+        final CompletableFuture<CommandSuggestions> result = new CompletableFuture<>();
+        CompletableFuture.allOf(futures).thenRun(() -> {
+            final Set<String> suggestions = Sets.newHashSet();
+            for (final CompletableFuture<Collection<String>> future : futures) {
+                suggestions.addAll(future.join());
+            }
+            final List<String> sorted = new ArrayList<>(suggestions);
+            Collections.sort(sorted);
+            result.complete(new CommandSuggestions(new StringRange(start, parse.getReader().getTotalLength()), sorted));
+        });
+
+        return result;
     }
 
     public RootCommandNode<S> getRoot() {
diff --git a/src/main/java/com/mojang/brigadier/arguments/ArgumentType.java b/src/main/java/com/mojang/brigadier/arguments/ArgumentType.java
index c7701ee..343757c 100644
--- a/src/main/java/com/mojang/brigadier/arguments/ArgumentType.java
+++ b/src/main/java/com/mojang/brigadier/arguments/ArgumentType.java
@@ -4,11 +4,14 @@ import com.mojang.brigadier.StringReader;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 
-import java.util.Set;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.concurrent.CompletableFuture;
 
 public interface ArgumentType<T> {
     <S> T parse(StringReader reader, CommandContextBuilder<S> contextBuilder) throws CommandSyntaxException;
 
-    default <S> void listSuggestions(final String command, final Set<String> output, final CommandContextBuilder<S> contextBuilder) {
+    default <S> CompletableFuture<Collection<String>> listSuggestions(final String command) {
+        return CompletableFuture.completedFuture(Collections.emptyList());
     }
 }
diff --git a/src/main/java/com/mojang/brigadier/tree/ArgumentCommandNode.java b/src/main/java/com/mojang/brigadier/tree/ArgumentCommandNode.java
index b9ef2b9..6e60765 100644
--- a/src/main/java/com/mojang/brigadier/tree/ArgumentCommandNode.java
+++ b/src/main/java/com/mojang/brigadier/tree/ArgumentCommandNode.java
@@ -5,14 +5,12 @@ import com.mojang.brigadier.RedirectModifier;
 import com.mojang.brigadier.StringReader;
 import com.mojang.brigadier.arguments.ArgumentType;
 import com.mojang.brigadier.builder.RequiredArgumentBuilder;
-import com.mojang.brigadier.context.CommandContext;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.context.ParsedArgument;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 
 import java.util.Collection;
-import java.util.Set;
-import java.util.function.Function;
+import java.util.concurrent.CompletableFuture;
 import java.util.function.Predicate;
 
 public class ArgumentCommandNode<S, T> extends CommandNode<S> {
@@ -57,8 +55,8 @@ public class ArgumentCommandNode<S, T> extends CommandNode<S> {
     }
 
     @Override
-    public void listSuggestions(final String command, final Set<String> output, final CommandContextBuilder<S> contextBuilder) {
-        type.listSuggestions(command, output, contextBuilder);
+    public CompletableFuture<Collection<String>> listSuggestions(final String command) {
+        return type.listSuggestions(command);
     }
 
     @Override
diff --git a/src/main/java/com/mojang/brigadier/tree/CommandNode.java b/src/main/java/com/mojang/brigadier/tree/CommandNode.java
index a75f824..a5f1262 100644
--- a/src/main/java/com/mojang/brigadier/tree/CommandNode.java
+++ b/src/main/java/com/mojang/brigadier/tree/CommandNode.java
@@ -14,6 +14,8 @@ import java.util.Collection;
 import java.util.LinkedHashMap;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
 import java.util.function.Function;
 import java.util.function.Predicate;
 import java.util.stream.Collectors;
@@ -97,7 +99,7 @@ public abstract class CommandNode<S> implements Comparable<CommandNode<S>> {
 
     public abstract void parse(StringReader reader, CommandContextBuilder<S> contextBuilder) throws CommandSyntaxException;
 
-    public abstract void listSuggestions(String command, Set<String> output, CommandContextBuilder<S> contextBuilder);
+    public abstract CompletableFuture<Collection<String>> listSuggestions(String command);
 
     public abstract ArgumentBuilder<S, ?> createBuilder();
 
diff --git a/src/main/java/com/mojang/brigadier/tree/LiteralCommandNode.java b/src/main/java/com/mojang/brigadier/tree/LiteralCommandNode.java
index c0bb9fe..1e1c20e 100644
--- a/src/main/java/com/mojang/brigadier/tree/LiteralCommandNode.java
+++ b/src/main/java/com/mojang/brigadier/tree/LiteralCommandNode.java
@@ -4,15 +4,16 @@ import com.mojang.brigadier.Command;
 import com.mojang.brigadier.RedirectModifier;
 import com.mojang.brigadier.StringReader;
 import com.mojang.brigadier.builder.LiteralArgumentBuilder;
-import com.mojang.brigadier.context.CommandContext;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.context.StringRange;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 import com.mojang.brigadier.exceptions.ParameterizedCommandExceptionType;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Set;
-import java.util.function.Function;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Future;
 import java.util.function.Predicate;
 
 public class LiteralCommandNode<S> extends CommandNode<S> {
@@ -50,9 +51,11 @@ public class LiteralCommandNode<S> extends CommandNode<S> {
     }
 
     @Override
-    public void listSuggestions(final String command, final Set<String> output, final CommandContextBuilder<S> contextBuilder) {
+    public CompletableFuture<Collection<String>> listSuggestions(final String command) {
         if (literal.startsWith(command)) {
-            output.add(literal);
+            return CompletableFuture.completedFuture(Collections.singleton(literal));
+        } else {
+            return CompletableFuture.completedFuture(Collections.emptyList());
         }
     }
 
diff --git a/src/main/java/com/mojang/brigadier/tree/RootCommandNode.java b/src/main/java/com/mojang/brigadier/tree/RootCommandNode.java
index 01e2703..b531b91 100644
--- a/src/main/java/com/mojang/brigadier/tree/RootCommandNode.java
+++ b/src/main/java/com/mojang/brigadier/tree/RootCommandNode.java
@@ -5,8 +5,9 @@ import com.mojang.brigadier.builder.ArgumentBuilder;
 import com.mojang.brigadier.context.CommandContextBuilder;
 import com.mojang.brigadier.exceptions.CommandSyntaxException;
 
+import java.util.Collection;
 import java.util.Collections;
-import java.util.Set;
+import java.util.concurrent.CompletableFuture;
 
 public class RootCommandNode<S> extends CommandNode<S> {
     public RootCommandNode() {
@@ -28,7 +29,8 @@ public class RootCommandNode<S> extends CommandNode<S> {
     }
 
     @Override
-    public void listSuggestions(final String command, final Set<String> output, final CommandContextBuilder<S> contextBuilder) {
+    public CompletableFuture<Collection<String>> listSuggestions(final String command) {
+        return CompletableFuture.completedFuture(Collections.emptyList());
     }
 
     @Override
diff --git a/src/test/java/com/mojang/brigadier/CommandSuggestionsTest.java b/src/test/java/com/mojang/brigadier/CommandSuggestionsTest.java
index e0eaf67..be01a55 100644
--- a/src/test/java/com/mojang/brigadier/CommandSuggestionsTest.java
+++ b/src/test/java/com/mojang/brigadier/CommandSuggestionsTest.java
@@ -29,7 +29,7 @@ public class CommandSuggestionsTest {
         subject.register(literal("bar"));
         subject.register(literal("baz"));
 
-        final CommandSuggestions result = subject.getCompletionSuggestions(subject.parse("", source));
+        final CommandSuggestions result = subject.getCompletionSuggestions(subject.parse("", source)).join();
 
         assertThat(result.getRange(), equalTo(new StringRange(0, 0)));
         assertThat(result.getSuggestions(), equalTo(Lists.newArrayList("bar", "baz", "foo")));
@@ -41,7 +41,7 @@ public class CommandSuggestionsTest {
         subject.register(literal("bar"));
         subject.register(literal("baz"));
 
-        final CommandSuggestions result = subject.getCompletionSuggestions(subject.parse("b", source));
+        final CommandSuggestions result = subject.getCompletionSuggestions(subject.parse("b", source)).join();
 
         assertThat(result.getRange(), equalTo(new StringRange(0, 1)));
         assertThat(result.getSuggestions(), equalTo(Lists.newArrayList("bar", "baz")));
@@ -56,7 +56,7 @@ public class CommandSuggestionsTest {
                 .then(literal("baz"))
         );
 
-        final CommandSuggestions result = subject.getCompletionSuggestions(subject.parse("parent ", source));
+        final CommandSuggestions result = subject.getCompletionSuggestions(subject.parse("parent ", source)).join();
 
         assertThat(result.getRange(), equalTo(new StringRange(7, 7)));
         assertThat(result.getSuggestions(), equalTo(Lists.newArrayList("bar", "baz", "foo")));
@@ -71,7 +71,7 @@ public class CommandSuggestionsTest {
                 .then(literal("baz"))
         );
 
-        final CommandSuggestions result = subject.getCompletionSuggestions(subject.parse("parent b", source));
+        final CommandSuggestions result = subject.getCompletionSuggestions(subject.parse("parent b", source)).join();
 
         assertThat(result.getRange(), equalTo(new StringRange(7, 8)));
         assertThat(result.getSuggestions(), equalTo(Lists.newArrayList("bar", "baz")));
diff --git a/src/test/java/com/mojang/brigadier/arguments/FloatArgumentTypeTest.java b/src/test/java/com/mojang/brigadier/arguments/FloatArgumentTypeTest.java
index c6a7c31..d0cef81 100644
--- a/src/test/java/com/mojang/brigadier/arguments/FloatArgumentTypeTest.java
+++ b/src/test/java/com/mojang/brigadier/arguments/FloatArgumentTypeTest.java
@@ -67,14 +67,6 @@ public class FloatArgumentTypeTest {
         }
     }
 
-    @Test
-    public void testSuggestions() throws Exception {
-        final Set<String> set = Sets.newHashSet();
-        @SuppressWarnings("unchecked") final CommandContextBuilder<Object> context = Mockito.mock(CommandContextBuilder.class);
-        type.listSuggestions("", set, context);
-        assertThat(set, is(empty()));
-    }
-
     @Test
     public void testEquals() throws Exception {
         new EqualsTester()
diff --git a/src/test/java/com/mojang/brigadier/arguments/IntegerArgumentTypeTest.java b/src/test/java/com/mojang/brigadier/arguments/IntegerArgumentTypeTest.java
index 6dd3820..ea8bf08 100644
--- a/src/test/java/com/mojang/brigadier/arguments/IntegerArgumentTypeTest.java
+++ b/src/test/java/com/mojang/brigadier/arguments/IntegerArgumentTypeTest.java
@@ -13,6 +13,7 @@ import org.mockito.Mock;
 import org.mockito.Mockito;
 import org.mockito.runners.MockitoJUnitRunner;
 
+import java.util.Collection;
 import java.util.Set;
 
 import static com.mojang.brigadier.arguments.IntegerArgumentType.integer;
@@ -69,10 +70,8 @@ public class IntegerArgumentTypeTest {
 
     @Test
     public void testSuggestions() throws Exception {
-        final Set<String> set = Sets.newHashSet();
-        @SuppressWarnings("unchecked") final CommandContextBuilder<Object> context = Mockito.mock(CommandContextBuilder.class);
-        type.listSuggestions("", set, context);
-        assertThat(set, is(empty()));
+        final Collection<String> result = type.listSuggestions("").join();
+        assertThat(result, is(empty()));
     }
 
     @Test
diff --git a/src/test/java/com/mojang/brigadier/arguments/StringArgumentTypeTest.java b/src/test/java/com/mojang/brigadier/arguments/StringArgumentTypeTest.java
index ec5f0ed..6e4eff1 100644
--- a/src/test/java/com/mojang/brigadier/arguments/StringArgumentTypeTest.java
+++ b/src/test/java/com/mojang/brigadier/arguments/StringArgumentTypeTest.java
@@ -51,13 +51,6 @@ public class StringArgumentTypeTest {
         assertThat(reader.canRead(), is(false));
     }
 
-    @Test
-    public void testSuggestions() throws Exception {
-        final Set<String> set = Sets.newHashSet();
-        string().listSuggestions("", set, context);
-        assertThat(set, is(empty()));
-    }
-
     @Test
     public void testToString() throws Exception {
         assertThat(string(), hasToString("string()"));
diff --git a/src/test/java/com/mojang/brigadier/tree/ArgumentCommandNodeTest.java b/src/test/java/com/mojang/brigadier/tree/ArgumentCommandNodeTest.java
index ec11cfb..aff7b10 100644
--- a/src/test/java/com/mojang/brigadier/tree/ArgumentCommandNodeTest.java
+++ b/src/test/java/com/mojang/brigadier/tree/ArgumentCommandNodeTest.java
@@ -12,6 +12,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mockito;
 
+import java.util.Collection;
 import java.util.Set;
 
 import static com.mojang.brigadier.arguments.IntegerArgumentType.integer;
@@ -53,10 +54,8 @@ public class ArgumentCommandNodeTest extends AbstractCommandNodeTest {
 
     @Test
     public void testSuggestions() throws Exception {
-        final Set<String> set = Sets.newHashSet();
-        @SuppressWarnings("unchecked") final CommandContextBuilder<Object> context = Mockito.mock(CommandContextBuilder.class);
-        node.listSuggestions("", set, context);
-        assertThat(set, is(empty()));
+        final Collection<String> result = node.listSuggestions("").join();
+        assertThat(result, is(empty()));
     }
 
     @Test
diff --git a/src/test/java/com/mojang/brigadier/tree/LiteralCommandNodeTest.java b/src/test/java/com/mojang/brigadier/tree/LiteralCommandNodeTest.java
index b719213..ed49a54 100644
--- a/src/test/java/com/mojang/brigadier/tree/LiteralCommandNodeTest.java
+++ b/src/test/java/com/mojang/brigadier/tree/LiteralCommandNodeTest.java
@@ -13,6 +13,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mockito;
 
+import java.util.Collection;
 import java.util.Set;
 
 import static com.mojang.brigadier.builder.LiteralArgumentBuilder.literal;
@@ -80,23 +81,17 @@ public class LiteralCommandNodeTest extends AbstractCommandNodeTest {
 
     @Test
     public void testSuggestions() throws Exception {
-        final Set<String> set = Sets.newHashSet();
-        @SuppressWarnings("unchecked") final CommandContextBuilder<Object> context = Mockito.mock(CommandContextBuilder.class);
+        final Collection<String> empty = node.listSuggestions("").join();
+        assertThat(empty, equalTo(Sets.newHashSet("foo")));
 
-        node.listSuggestions("", set, context);
-        assertThat(set, equalTo(Sets.newHashSet("foo")));
+        final Collection<String> foo = node.listSuggestions("foo").join();
+        assertThat(foo, equalTo(Sets.newHashSet("foo")));
 
-        set.clear();
-        node.listSuggestions("foo", set, context);
-        assertThat(set, equalTo(Sets.newHashSet("foo")));
+        final Collection<String> food = node.listSuggestions("food").join();
+        assertThat(food, is(empty()));
 
-        set.clear();
-        node.listSuggestions("food", set, context);
-        assertThat(set, is(empty()));
-
-        set.clear();
-        node.listSuggestions("b", set, context);
-        assertThat(set, is(empty()));
+        final Collection<String> b = node.listSuggestions("b").join();
+        assertThat(b, is(empty()));
     }
 
     @Test
diff --git a/src/test/java/com/mojang/brigadier/tree/RootCommandNodeTest.java b/src/test/java/com/mojang/brigadier/tree/RootCommandNodeTest.java
index ab183fa..8de1fcb 100644
--- a/src/test/java/com/mojang/brigadier/tree/RootCommandNodeTest.java
+++ b/src/test/java/com/mojang/brigadier/tree/RootCommandNodeTest.java
@@ -9,6 +9,7 @@ import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mockito;
 
+import java.util.Collection;
 import java.util.Set;
 
 import static com.mojang.brigadier.builder.LiteralArgumentBuilder.literal;
@@ -48,10 +49,8 @@ public class RootCommandNodeTest extends AbstractCommandNodeTest {
 
     @Test
     public void testSuggestions() throws Exception {
-        final Set<String> set = Sets.newHashSet();
-        @SuppressWarnings("unchecked") final CommandContextBuilder<Object> context = Mockito.mock(CommandContextBuilder.class);
-        node.listSuggestions("", set, context);
-        assertThat(set, is(empty()));
+        final Collection<String> result = node.listSuggestions("").join();
+        assertThat(result, is(empty()));
     }
 
     @Test(expected = IllegalStateException.class)