diff --git a/lib/Coroutine.php b/lib/Coroutine.php
index 886f6b4..5a3b4aa 100644
--- a/lib/Coroutine.php
+++ b/lib/Coroutine.php
@@ -33,7 +33,6 @@ final class Coroutine implements Promise
 
         try {
             if (\is_array($yielded)) {
-                /** @var array<array-key, Promise|ReactPromise> $yielded */
                 return Promise\all($yielded);
             }
 
diff --git a/lib/Failure.php b/lib/Failure.php
index 8cf1b16..4c1ea62 100644
--- a/lib/Failure.php
+++ b/lib/Failure.php
@@ -7,7 +7,8 @@ use React\Promise\PromiseInterface as ReactPromise;
 /**
  * Creates a failed promise using the given exception.
  *
- * @template-implements Promise<?>
+ * @template-covariant TValue
+ * @template-implements Promise<TValue>
  */
 final class Failure implements Promise
 {
diff --git a/lib/Internal/Placeholder.php b/lib/Internal/Placeholder.php
index 6f50db7..b84aa70 100644
--- a/lib/Internal/Placeholder.php
+++ b/lib/Internal/Placeholder.php
@@ -70,9 +70,11 @@ trait Placeholder
         }
 
         if (!$this->onResolved instanceof ResolutionQueue) {
+            /** @psalm-suppress InternalClass */
             $this->onResolved = new ResolutionQueue($this->onResolved);
         }
 
+        /** @psalm-suppress InternalMethod */
         $this->onResolved->push($onResolved);
     }
 
diff --git a/lib/Internal/ResolutionQueue.php b/lib/Internal/ResolutionQueue.php
index 3bfc535..353a8b9 100644
--- a/lib/Internal/ResolutionQueue.php
+++ b/lib/Internal/ResolutionQueue.php
@@ -11,7 +11,7 @@ use React\Promise\PromiseInterface as ReactPromise;
  * Stores a set of functions to be invoked when a promise is resolved.
  *
  * @internal
- * @psalm-internal Amp
+ * @psalm-internal Amp\Internal
  */
 class ResolutionQueue
 {
diff --git a/lib/Loop/Driver.php b/lib/Loop/Driver.php
index 1c49b5e..57d6862 100644
--- a/lib/Loop/Driver.php
+++ b/lib/Loop/Driver.php
@@ -134,6 +134,7 @@ abstract class Driver
             }
         }
 
+        /** @psalm-suppress RedundantCondition */
         $this->dispatch(empty($this->nextTickQueue) && empty($this->enableQueue) && $this->running && !$this->isEmpty());
     }
 
diff --git a/lib/Loop/UvDriver.php b/lib/Loop/UvDriver.php
index 91ea5d9..a0d73c1 100644
--- a/lib/Loop/UvDriver.php
+++ b/lib/Loop/UvDriver.php
@@ -171,6 +171,7 @@ class UvDriver extends Driver
      */
     public function now(): int
     {
+        /** @psalm-suppress TooManyArguments */
         return \uv_now($this->handle);
     }
 
@@ -187,6 +188,7 @@ class UvDriver extends Driver
      */
     protected function dispatch(bool $blocking)
     {
+        /** @psalm-suppress TooManyArguments */
         \uv_run($this->handle, $blocking ? \UV::RUN_ONCE : \UV::RUN_NOWAIT);
     }
 
diff --git a/psalm.xml b/psalm.xml
index fe548ca..d6aa085 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <psalm
         totallyTyped="false"
-        errorLevel="5"
+        errorLevel="4"
         phpVersion="7.0"
         resolveFromConfigFile="true"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"