diff --git a/src/ContainerBuilder.php b/src/ContainerBuilder.php
index 1869b9e1e..cc8ad9038 100644
--- a/src/ContainerBuilder.php
+++ b/src/ContainerBuilder.php
@@ -100,6 +100,11 @@ class ContainerBuilder
      */
     private $sourceCache = false;
 
+    /**
+     * @var string
+     */
+    protected $sourceCacheNamespace;
+
     /**
      * Build a container configured for the dev environment.
      */
@@ -155,7 +160,7 @@ public function build()
                 throw new \Exception('APCu is not enabled, PHP-DI cannot use it as a cache');
             }
             // Wrap the source with the cache decorator
-            $source = new SourceCache($source);
+            $source = new SourceCache($source, $this->sourceCacheNamespace);
         }
 
         $proxyFactory = new ProxyFactory(
@@ -350,13 +355,15 @@ public function addDefinitions(...$definitions) : self
      *
      * @see http://php-di.org/doc/performances.html
      *
+     * @param string $cacheNamespace use unique namespace per container when sharing a single APC memory pool to prevent cache collisions
      * @return $this
      */
-    public function enableDefinitionCache() : self
+    public function enableDefinitionCache(string $cacheNamespace = '') : self
     {
         $this->ensureNotLocked();
 
         $this->sourceCache = true;
+        $this->sourceCacheNamespace = $cacheNamespace;
 
         return $this;
     }
diff --git a/src/Definition/Source/SourceCache.php b/src/Definition/Source/SourceCache.php
index 063b757c0..6487c2c0c 100644
--- a/src/Definition/Source/SourceCache.php
+++ b/src/Definition/Source/SourceCache.php
@@ -23,21 +23,27 @@ class SourceCache implements DefinitionSource, MutableDefinitionSource
      */
     private $cachedSource;
 
-    public function __construct(DefinitionSource $cachedSource)
+    /**
+     * @var string
+     */
+    private $cacheNamespace;
+
+    public function __construct(DefinitionSource $cachedSource, string $cacheNamespace = '')
     {
         $this->cachedSource = $cachedSource;
+        $this->cacheNamespace = $cacheNamespace;
     }
 
     public function getDefinition(string $name)
     {
-        $definition = apcu_fetch(self::CACHE_KEY . $name);
+        $definition = apcu_fetch($this->getCacheKey($name));
 
         if ($definition === false) {
             $definition = $this->cachedSource->getDefinition($name);
 
             // Update the cache
             if ($this->shouldBeCached($definition)) {
-                apcu_store(self::CACHE_KEY . $name, $definition);
+                apcu_store($this->getCacheKey($name), $definition);
             }
         }
 
@@ -59,6 +65,11 @@ public static function isSupported() : bool
             && ! ('cli' === \PHP_SAPI && ! ini_get('apc.enable_cli'));
     }
 
+    public function getCacheKey(string $name) : string
+    {
+        return self::CACHE_KEY . $this->cacheNamespace . $name;
+    }
+
     public function addDefinition(Definition $definition)
     {
         throw new \LogicException('You cannot set a definition at runtime on a container that has caching enabled. Doing so would risk caching the definition for the next execution, where it might be different. You can either put your definitions in a file, remove the cache or ->set() a raw value directly (PHP object, string, int, ...) instead of a PHP-DI definition.');
diff --git a/tests/UnitTest/ContainerBuilderTest.php b/tests/UnitTest/ContainerBuilderTest.php
index 9874d4526..8e2ebf9cc 100644
--- a/tests/UnitTest/ContainerBuilderTest.php
+++ b/tests/UnitTest/ContainerBuilderTest.php
@@ -58,6 +58,28 @@ public function should_allow_to_configure_a_cache()
         $this->assertInstanceOf(SourceCache::class, $container->definitionSource);
     }
 
+    /**
+     * @test
+     */
+    public function should_allow_to_configure_a_cache_with_a_namespace()
+    {
+        if (! SourceCache::isSupported()) {
+            $this->markTestSkipped('APCu extension is required');
+            return;
+        }
+
+        $namespace = 'staging';
+        $builder = new ContainerBuilder(FakeContainer::class);
+        $builder->enableDefinitionCache($namespace);
+
+        /** @var FakeContainer $container */
+        $container = $builder->build();
+        $source = $container->definitionSource;
+
+        $this->assertInstanceOf(SourceCache::class, $source);
+        $this->assertSame($source->getCacheKey('foo'), SourceCache::CACHE_KEY . $namespace . 'foo');
+    }
+
     /**
      * @test
      */
diff --git a/tests/UnitTest/Definition/Source/SourceCacheTest.php b/tests/UnitTest/Definition/Source/SourceCacheTest.php
index d619b92a8..47a39a536 100644
--- a/tests/UnitTest/Definition/Source/SourceCacheTest.php
+++ b/tests/UnitTest/Definition/Source/SourceCacheTest.php
@@ -90,6 +90,16 @@ public function should_only_cache_object_and_autowire_definitions()
         self::assertSame($definition, $source->getDefinition('foo'));
     }
 
+    /**
+     * @test
+     */
+    public function should_use_namespaced_cache_keys()
+    {
+        $namespace = 'staging';
+        $source = new SourceCache(new DefinitionArray, $namespace);
+        self::assertSame($source->getCacheKey('foo'), SourceCache::CACHE_KEY . $namespace . 'foo');
+    }
+
     private static function assertSavedInCache(string $definitionName, $expectedValue)
     {
         $definition = apcu_fetch(SourceCache::CACHE_KEY . $definitionName);