diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 50a61b3e..5e04fee0 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -11,6 +11,7 @@ jobs:
     name: "Unit tests"
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         dependencies: ["lowest", "highest"]
         extensions: [
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 236a9131..b00a8a62 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,7 @@
 
 All notable changes to this project will be documented in this file, in reverse chronological order by release.
 
-## 6.3.0 - TBC
+## 6.3.0 - 2021-06-17
 
 ### Added
 
@@ -10,7 +10,7 @@ All notable changes to this project will be documented in this file, in reverse
 
 ### Changed
 
-- Nothing.
+- [#226](https://github.com/scoutapp/scout-apm-php/pull/226) Increased recommended extension version to 1.4.0
 
 ### Deprecated
 
diff --git a/known-issues.xml b/known-issues.xml
index ec59d3d2..26553147 100644
--- a/known-issues.xml
+++ b/known-issues.xml
@@ -138,17 +138,6 @@
       <code>$this-&gt;value</code>
     </MixedReturnStatement>
   </file>
-  <file src="src/Extension/PotentiallyAvailableExtensionCapabilities.php">
-    <MixedArgument occurrences="1">
-      <code>scoutapm_get_calls()</code>
-    </MixedArgument>
-    <MixedArgumentTypeCoercion occurrences="1">
-      <code>$call</code>
-    </MixedArgumentTypeCoercion>
-    <MixedReturnTypeCoercion occurrences="2">
-      <code>list&lt;RecordedCall&gt;</code>
-    </MixedReturnTypeCoercion>
-  </file>
   <file src="src/Helper/Backtrace.php">
     <MixedArgument occurrences="1">
       <code>$composerContent['config']</code>
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
index 26d00837..6d4c1c1c 100644
--- a/phpcs.xml.dist
+++ b/phpcs.xml.dist
@@ -18,4 +18,7 @@
     <rule ref="Doctrine">
         <exclude name="Generic.Files.LineLength.TooLong"/>
     </rule>
+    <rule ref="PSR1.Files.SideEffects.FoundWithSymbols">
+        <exclude-pattern>src/Extension/ExtensionCapabilities.php</exclude-pattern>
+    </rule>
 </ruleset>
diff --git a/src/Agent.php b/src/Agent.php
index f0f16e6e..1c56e3e2 100644
--- a/src/Agent.php
+++ b/src/Agent.php
@@ -29,7 +29,7 @@
 use Scoutapm\Events\Span\Span;
 use Scoutapm\Events\Span\SpanReference;
 use Scoutapm\Events\Tag\Tag;
-use Scoutapm\Extension\ExtentionCapabilities;
+use Scoutapm\Extension\ExtensionCapabilities;
 use Scoutapm\Extension\PotentiallyAvailableExtensionCapabilities;
 use Scoutapm\Extension\Version;
 use Scoutapm\Helper\LocateFileOrFolder;
@@ -51,7 +51,7 @@ final class Agent implements ScoutApmAgent
 
     private const METADATA_CACHE_TTL_SECONDS = 600;
 
-    private const WARN_WHEN_EXTENSION_IS_OLDER_THAN = '1.0.2';
+    private const WARN_WHEN_EXTENSION_IS_OLDER_THAN = '1.4.0';
 
     /** @var Config */
     private $config;
@@ -65,7 +65,7 @@ final class Agent implements ScoutApmAgent
     private $ignoredEndpoints;
     /** @var bool If this request was marked as ignored*/
     private $isIgnored = false;
-    /** @var ExtentionCapabilities */
+    /** @var ExtensionCapabilities */
     private $phpExtension;
     /** @var CacheInterface */
     private $cache;
@@ -80,7 +80,7 @@ private function __construct(
         Config $configuration,
         Connector $connector,
         LoggerInterface $logger,
-        ExtentionCapabilities $phpExtension,
+        ExtensionCapabilities $phpExtension,
         CacheInterface $cache,
         LocateFileOrFolder $locateFileOrFolder
     ) {
@@ -136,14 +136,14 @@ public static function fromConfig(
         LoggerInterface $logger,
         ?CacheInterface $cache = null,
         ?Connector $connector = null,
-        ?ExtentionCapabilities $extentionCapabilities = null,
+        ?ExtensionCapabilities $extensionCapabilities = null,
         ?LocateFileOrFolder $locateFileOrFolder = null
     ): self {
         return new self(
             $config,
             $connector ?? self::createConnectorFromConfig($config),
             $logger,
-            $extentionCapabilities ?? new PotentiallyAvailableExtensionCapabilities(),
+            $extensionCapabilities ?? new PotentiallyAvailableExtensionCapabilities(),
             $cache ?? new DevNullCache(),
             $locateFileOrFolder ?? new LocateFileOrFolder()
         );
diff --git a/src/Events/Metadata.php b/src/Events/Metadata.php
index 00ba06c0..48f1096e 100644
--- a/src/Events/Metadata.php
+++ b/src/Events/Metadata.php
@@ -9,7 +9,7 @@
 use Scoutapm\Config;
 use Scoutapm\Config\ConfigKey;
 use Scoutapm\Connector\Command;
-use Scoutapm\Extension\ExtentionCapabilities;
+use Scoutapm\Extension\ExtensionCapabilities;
 use Scoutapm\Helper\LocateFileOrFolder;
 use Scoutapm\Helper\Timer;
 
@@ -40,7 +40,7 @@ final class Metadata implements Command
     private $timer;
     /** @var Config */
     private $config;
-    /** @var ExtentionCapabilities */
+    /** @var ExtensionCapabilities */
     private $phpExtension;
     /** @var LocateFileOrFolder */
     private $locateFileOrFolder;
@@ -48,7 +48,7 @@ final class Metadata implements Command
     public function __construct(
         DateTimeImmutable $now,
         Config $config,
-        ExtentionCapabilities $phpExtension,
+        ExtensionCapabilities $phpExtension,
         LocateFileOrFolder $locateFileOrFolder
     ) {
         // Construct and stop the timer to use its timestamp logic. This event
diff --git a/src/Extension/ExtentionCapabilities.php b/src/Extension/ExtensionCapabilities.php
similarity index 65%
rename from src/Extension/ExtentionCapabilities.php
rename to src/Extension/ExtensionCapabilities.php
index 9af04235..a2d06d37 100644
--- a/src/Extension/ExtentionCapabilities.php
+++ b/src/Extension/ExtensionCapabilities.php
@@ -4,7 +4,9 @@
 
 namespace Scoutapm\Extension;
 
-interface ExtentionCapabilities
+use function class_alias;
+
+interface ExtensionCapabilities
 {
     /** @return RecordedCall[]|array<int, RecordedCall> */
     public function getCalls(): array;
@@ -13,3 +15,5 @@ public function clearRecordedCalls(): void;
 
     public function version(): ?Version;
 }
+
+class_alias(ExtensionCapabilities::class, ExtentionCapabilities::class);
diff --git a/src/Extension/PotentiallyAvailableExtensionCapabilities.php b/src/Extension/PotentiallyAvailableExtensionCapabilities.php
index 8ab487ad..3dd051cd 100644
--- a/src/Extension/PotentiallyAvailableExtensionCapabilities.php
+++ b/src/Extension/PotentiallyAvailableExtensionCapabilities.php
@@ -12,8 +12,22 @@
 use function phpversion;
 use function scoutapm_get_calls;
 
-final class PotentiallyAvailableExtensionCapabilities implements ExtentionCapabilities
+final class PotentiallyAvailableExtensionCapabilities implements ExtensionCapabilities
 {
+    public function __construct()
+    {
+        if (! $this->extensionIsAvailable()) {
+            return;
+        }
+
+        // If the function doesn't exist, we're probably using an older `scoutapm` extension which doesn't need enabling
+        if (! function_exists('scoutapm_enable_instrumentation')) {
+            return;
+        }
+
+        scoutapm_enable_instrumentation(true);
+    }
+
     /**
      * @return RecordedCall[]
      *
diff --git a/src/Extension/Version.php b/src/Extension/Version.php
index f6514b25..dc910471 100644
--- a/src/Extension/Version.php
+++ b/src/Extension/Version.php
@@ -53,21 +53,8 @@ public static function fromString(string $versionString): self
 
     public function isOlderThan(self $otherVersion): bool
     {
-        if ($this->major > $otherVersion->major) {
-            return false;
-        }
-
-        if ($this->minor > $otherVersion->minor) {
-            return false;
-        }
-
-        if ($this->patch > $otherVersion->patch) {
-            return false;
-        }
-
-        return $otherVersion->major > $this->major
-            || $otherVersion->minor > $this->minor
-            || $otherVersion->patch > $this->patch;
+        return (($this->major * 1000000) + ($this->minor * 1000) + $this->patch)
+            < (($otherVersion->major * 1000000) + ($otherVersion->minor * 1000) + $otherVersion->patch);
     }
 
     public function toString(): string
diff --git a/src/ScoutApmBundle/ScoutApmAgentFactory.php b/src/ScoutApmBundle/ScoutApmAgentFactory.php
index 19af93f9..919caede 100644
--- a/src/ScoutApmBundle/ScoutApmAgentFactory.php
+++ b/src/ScoutApmBundle/ScoutApmAgentFactory.php
@@ -9,7 +9,7 @@
 use Scoutapm\Agent;
 use Scoutapm\Config;
 use Scoutapm\Connector\Connector;
-use Scoutapm\Extension\ExtentionCapabilities;
+use Scoutapm\Extension\ExtensionCapabilities;
 use Scoutapm\ScoutApmAgent;
 use Symfony\Component\HttpKernel\Kernel;
 
@@ -25,7 +25,7 @@ public static function createAgent(
         LoggerInterface $logger,
         ?CacheInterface $cache,
         ?Connector $connector,
-        ?ExtentionCapabilities $extentionCapabilities,
+        ?ExtensionCapabilities $extensionCapabilities,
         array $agentConfiguration
     ): ScoutApmAgent {
         return Agent::fromConfig(
@@ -39,7 +39,7 @@ public static function createAgent(
             $logger,
             $cache,
             $connector,
-            $extentionCapabilities
+            $extensionCapabilities
         );
     }
 }
diff --git a/tests/Unit/AgentTest.php b/tests/Unit/AgentTest.php
index 3df1adfb..1046a4d5 100644
--- a/tests/Unit/AgentTest.php
+++ b/tests/Unit/AgentTest.php
@@ -28,7 +28,7 @@
 use Scoutapm\Events\Span\SpanReference;
 use Scoutapm\Events\Tag\Tag;
 use Scoutapm\Events\Tag\TagRequest;
-use Scoutapm\Extension\ExtentionCapabilities;
+use Scoutapm\Extension\ExtensionCapabilities;
 use Scoutapm\Extension\RecordedCall;
 use Scoutapm\Extension\Version;
 use Scoutapm\IntegrationTests\TestHelper;
@@ -54,7 +54,7 @@ final class AgentTest extends TestCase
     /** @var Connector&MockObject */
     private $connector;
 
-    /** @var ExtentionCapabilities&MockObject */
+    /** @var ExtensionCapabilities&MockObject */
     private $phpExtension;
 
     public function setUp(): void
@@ -63,7 +63,7 @@ public function setUp(): void
 
         $this->logger       = new TestLogger();
         $this->connector    = $this->createMock(Connector::class);
-        $this->phpExtension = $this->createMock(ExtentionCapabilities::class);
+        $this->phpExtension = $this->createMock(ExtensionCapabilities::class);
     }
 
     private function requestFromAgent(ScoutApmAgent $agent): ?Request
diff --git a/tests/Unit/Events/MetadataTest.php b/tests/Unit/Events/MetadataTest.php
index 51824da2..5f4c760b 100644
--- a/tests/Unit/Events/MetadataTest.php
+++ b/tests/Unit/Events/MetadataTest.php
@@ -13,7 +13,7 @@
 use Scoutapm\Config;
 use Scoutapm\Config\ConfigKey;
 use Scoutapm\Events\Metadata;
-use Scoutapm\Extension\ExtentionCapabilities;
+use Scoutapm\Extension\ExtensionCapabilities;
 use Scoutapm\Extension\Version;
 use Scoutapm\Helper\LocateFileOrFolder;
 use Scoutapm\Helper\Timer;
@@ -33,7 +33,7 @@
  */
 final class MetadataTest extends TestCase
 {
-    /** @var ExtentionCapabilities&MockObject */
+    /** @var ExtensionCapabilities&MockObject */
     private $phpExtension;
     /** @var LocateFileOrFolder&MockObject */
     private $locateFileOrFolder;
@@ -44,7 +44,7 @@ public function setUp(): void
     {
         parent::setUp();
 
-        $this->phpExtension       = $this->createMock(ExtentionCapabilities::class);
+        $this->phpExtension       = $this->createMock(ExtensionCapabilities::class);
         $this->locateFileOrFolder = $this->createMock(LocateFileOrFolder::class);
 
         $this->time = new DateTimeImmutable('now', new DateTimeZone('UTC'));
diff --git a/tests/Unit/Extension/VersionTest.php b/tests/Unit/Extension/VersionTest.php
index 5ec884a1..2e46d134 100644
--- a/tests/Unit/Extension/VersionTest.php
+++ b/tests/Unit/Extension/VersionTest.php
@@ -27,6 +27,7 @@ public function olderThanVersionProvider(): array
             ['testVersion' => '1.0.0', 'isOlderThan' => '1.0.0', 'expectedResult' => false],
             ['testVersion' => '1.1.0', 'isOlderThan' => '1.1.0', 'expectedResult' => false],
             ['testVersion' => '1.1.1', 'isOlderThan' => '1.1.1', 'expectedResult' => false],
+            ['testVersion' => '1.3.0', 'isOlderThan' => '0.0.1', 'expectedResult' => false],
             ['testVersion' => '2.0.0', 'isOlderThan' => '1.0.2', 'expectedResult' => false],
             ['testVersion' => '2.0.0', 'isOlderThan' => '1.2.0', 'expectedResult' => false],
         ];
diff --git a/tests/Unit/ScoutApmBundle/ScoutApmAgentFactoryTest.php b/tests/Unit/ScoutApmBundle/ScoutApmAgentFactoryTest.php
index ce6e9dc8..c3e7ffe3 100644
--- a/tests/Unit/ScoutApmBundle/ScoutApmAgentFactoryTest.php
+++ b/tests/Unit/ScoutApmBundle/ScoutApmAgentFactoryTest.php
@@ -10,7 +10,7 @@
 use Scoutapm\Config\ConfigKey;
 use Scoutapm\Connector\Connector;
 use Scoutapm\Events\Metadata;
-use Scoutapm\Extension\ExtentionCapabilities;
+use Scoutapm\Extension\ExtensionCapabilities;
 use Scoutapm\ScoutApmBundle\ScoutApmAgentFactory;
 
 use function json_decode;
@@ -24,7 +24,7 @@ public function testFactoryConfiguresFrameworkNameAndVersion(): void
         $logger       = $this->createMock(LoggerInterface::class);
         $cache        = $this->createMock(CacheInterface::class);
         $connector    = $this->createMock(Connector::class);
-        $phpExtension = $this->createMock(ExtentionCapabilities::class);
+        $phpExtension = $this->createMock(ExtensionCapabilities::class);
 
         $connector->expects(self::at(3))
             ->method('sendCommand')
diff --git a/tests/psalm-stubs.php b/tests/psalm-stubs.php
index dadadaf3..317bdbaf 100644
--- a/tests/psalm-stubs.php
+++ b/tests/psalm-stubs.php
@@ -3,6 +3,22 @@
 /** @noinspection PhpIllegalPsrClassPathInspection */
 declare(strict_types=1);
 
+namespace {
+    function scoutapm_enable_instrumentation(bool $enabled): void
+    {
+    }
+
+    /** @psalm-return list<array{function:string, entered:float, exited: float, time_taken: float, argv: mixed[]}> */
+    function scoutapm_get_calls(): array
+    {
+    }
+
+    /** @return list<string> */
+    function scoutapm_list_instrumented_functions(): array
+    {
+    }
+}
+
 namespace Composer {
     class InstalledVersions {
         /**