diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 1611b8b..089364a 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -18,6 +18,7 @@ jobs:
           php-version: 8.2
           extensions: xdebug
           tools: composer:2
+          ini-file: development
       - name: Setup problem matchers for PHP
         run: echo "::add-matcher::${{ runner.tool_cache }}/php.json"
       - name: Setup problem matchers for PHPUnit
diff --git a/src/Definition/Serializer/XmlContainerDefinitionSerializer.php b/src/Definition/Serializer/XmlContainerDefinitionSerializer.php
index 0d261b0..bffee78 100644
--- a/src/Definition/Serializer/XmlContainerDefinitionSerializer.php
+++ b/src/Definition/Serializer/XmlContainerDefinitionSerializer.php
@@ -305,7 +305,10 @@ private function addServiceDefinitionsToBuilder(ContainerDefinitionBuilder $buil
 
         foreach ($serviceDefinitions as $serviceDefinition) {
             $serviceType = $xpath->query('cd:type/text()', $serviceDefinition)[0]->nodeValue;
-            assert(class_exists($serviceType));
+            assert(
+                class_exists($serviceType) || interface_exists($serviceType),
+                "The type $serviceType does not exist"
+            );
             $isConcrete = $xpath->query('@isConcrete', $serviceDefinition)[0]->nodeValue === 'true';
             $attr = unserialize(base64_decode(
                 $xpath->query('cd:attribute/text()', $serviceDefinition)[0]?->nodeValue
@@ -331,7 +334,11 @@ private function addAliasDefinitionsToBuilder(ContainerDefinitionBuilder $builde
             $abstract = $xpath->query('cd:abstractService/text()', $aliasDefinition)[0]->nodeValue;
             $concrete = $xpath->query('cd:concreteService/text()', $aliasDefinition)[0]->nodeValue;
 
-            assert(class_exists($abstract));
+            assert(
+                class_exists($abstract) || interface_exists($abstract),
+                "The type $abstract does not exist"
+            );
+            // we are not checking for interface_exists() here because an interface cannot be a concrete service
             assert(class_exists($concrete));
 
             $builder = $builder->withAliasDefinition(
@@ -351,7 +358,10 @@ private function addServicePrepareDefinitionsToBuilder(ContainerDefinitionBuilde
             $method = $xpath->query('cd:method/text()', $prepareDefinition)[0]->nodeValue;
             $attr = unserialize(base64_decode($xpath->query('cd:attribute/text()', $prepareDefinition)[0]?->nodeValue));
 
-            assert(class_exists($service));
+            assert(
+                class_exists($service) || interface_exists($service),
+                "The type $service does not exist"
+            );
             assert($method !== null && $method !== '');
 
             $builder = $builder->withServicePrepareDefinition(
@@ -372,7 +382,11 @@ private function addServiceDelegateDefinitionsToBuilder(ContainerDefinitionBuild
             $delegateMethod = $xpath->query('cd:delegateMethod/text()', $delegateDefinition)[0]->nodeValue;
             $attr = unserialize(base64_decode($xpath->query('cd:attribute/text()', $delegateDefinition)[0]?->nodeValue));
 
-            assert(class_exists($service));
+            assert(
+                class_exists($service) || interface_exists($service),
+                "The type $service does not exist"
+            );
+            // we are not checking for interface_exists() because a delegate must be a concrete type
             assert(class_exists($delegateType));
             assert($delegateMethod !== null && $delegateMethod !== '');
 
diff --git a/src/LogicalConstraint/Check/MultiplePrimaryForAbstractService.php b/src/LogicalConstraint/Check/MultiplePrimaryForAbstractService.php
index 76c1cb9..32cef28 100644
--- a/src/LogicalConstraint/Check/MultiplePrimaryForAbstractService.php
+++ b/src/LogicalConstraint/Check/MultiplePrimaryForAbstractService.php
@@ -68,7 +68,10 @@ private function getConcreteServicesInstanceOf(ContainerDefinition $containerDef
         foreach ($containerDefinition->serviceDefinitions() as $service) {
             if ($service->isConcrete()) {
                 $serviceDefinitionType = $serviceDefinition->type()->name();
-                assert(class_exists($serviceDefinitionType));
+                assert(
+                    class_exists($serviceDefinitionType) || interface_exists($serviceDefinitionType),
+                    "The type $serviceDefinitionType does not exist"
+                );
                 if (is_subclass_of($service->type()->name(), $serviceDefinitionType)) {
                     yield $service;
                 }
diff --git a/src/Reflection/TypeFactory.php b/src/Reflection/TypeFactory.php
index 13510b7..a43a443 100644
--- a/src/Reflection/TypeFactory.php
+++ b/src/Reflection/TypeFactory.php
@@ -57,7 +57,10 @@ public function fromName(string $name) : Type {
             default => null,
         };
         if ($type === null) {
-            assert(class_exists($name));
+            assert(
+                class_exists($name) || interface_exists($name),
+                "The type $name does not exist"
+            );
             $type = $this->class($name);
         }
 
diff --git a/src/StaticAnalysis/AnnotatedTargetContainerDefinitionAnalyzer.php b/src/StaticAnalysis/AnnotatedTargetContainerDefinitionAnalyzer.php
index 5b8ed93..cf5cfb0 100644
--- a/src/StaticAnalysis/AnnotatedTargetContainerDefinitionAnalyzer.php
+++ b/src/StaticAnalysis/AnnotatedTargetContainerDefinitionAnalyzer.php
@@ -189,7 +189,10 @@ private function addAnnotatedDefinitions(
             foreach ($abstractPrepareDefinitions as $abstractPrepareDefinition) {
                 $concreteServiceName = $concretePrepareDefinition->service()->name();
                 $abstractServiceName = $abstractPrepareDefinition->service()->name();
-                assert(class_exists($abstractServiceName));
+                assert(
+                    class_exists($abstractServiceName) || interface_exists($abstractServiceName),
+                    "The type $abstractServiceName does not exist"
+                );
                 if (is_subclass_of($concreteServiceName, $abstractServiceName)) {
                     $hasAbstractPrepare = true;
                     break;
@@ -277,9 +280,12 @@ private function addAliasDefinitions(ContainerDefinitionBuilder $containerDefini
         }
 
         foreach ($abstractTypes as $abstractType) {
+            $abstractTypeString = $abstractType->name();
+            assert(
+                class_exists($abstractTypeString) || interface_exists($abstractTypeString),
+                "The type $abstractTypeString does not exist"
+            );
             foreach ($concreteTypes as $concreteType) {
-                $abstractTypeString = $abstractType->name();
-                assert(class_exists($abstractTypeString), "The type $abstractTypeString does not exist");
                 if (is_subclass_of($concreteType->name(), $abstractTypeString)) {
                     $aliasDefinition = definitionFactory()->aliasDefinition($abstractType, $concreteType);
                     $containerDefinitionBuilder = $containerDefinitionBuilder->withAliasDefinition($aliasDefinition);