diff --git a/src/Server/TextDocument.php b/src/Server/TextDocument.php
index 532d642..624bc67 100644
--- a/src/Server/TextDocument.php
+++ b/src/Server/TextDocument.php
@@ -412,7 +412,7 @@ class TextDocument
             if (preg_match('/\/vendor\/([^\/]+\/[^\/]+)\//', $def->symbolInformation->location->uri, $matches) && $this->composerLock !== null) {
                 // Definition is inside a dependency
                 $packageName = $matches[1];
-                foreach ($this->composerLock->packages as $package) {
+                foreach (array_merge($this->composerLock->packages, $this->composerLock->{'packages-dev'}) as $package) {
                     if ($package->name === $packageName) {
                         $symbol->package = $package;
                         break;
diff --git a/src/Server/Workspace.php b/src/Server/Workspace.php
index 5aae7cf..5c0e9fa 100644
--- a/src/Server/Workspace.php
+++ b/src/Server/Workspace.php
@@ -124,7 +124,7 @@ class Workspace
                     // Find out package name
                     preg_match('/\/vendor\/([^\/]+\/[^\/]+)\//', $def->symbolInformation->location->uri, $matches);
                     $packageName = $matches[1];
-                    foreach ($this->composerLock->packages as $package) {
+                    foreach (array_merge($this->composerLock->packages, $this->composerLock->{'packages-dev'}) as $package) {
                         if ($package->name === $packageName) {
                             $symbol->package = $package;
                             break;
@@ -165,7 +165,7 @@ class Workspace
             return [];
         }
         $dependencyReferences = [];
-        foreach ($this->composerLock->packages as $package) {
+        foreach (array_merge($this->composerLock->packages, $this->composerLock->{'packages-dev'}) as $package) {
             $dependencyReferences[] = new DependencyReference($package);
         }
         return $dependencyReferences;