diff --git a/src/Symfony/Component/DependencyInjection/Container.php b/src/Symfony/Component/DependencyInjection/Container.php
index 2d43ba7a60..c878af3d9e 100644
--- a/src/Symfony/Component/DependencyInjection/Container.php
+++ b/src/Symfony/Component/DependencyInjection/Container.php
@@ -199,16 +199,16 @@ class Container implements ResettableContainerInterface
 
         if (isset($this->privates[$id])) {
             if (null === $service) {
-                @trigger_error(sprintf('Unsetting the "%s" private service is deprecated since Symfony 3.2 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
+                @trigger_error(sprintf('The "%s" service is private, unsetting it is deprecated since Symfony 3.2 and will fail in 4.0.', $id), E_USER_DEPRECATED);
                 unset($this->privates[$id]);
             } else {
-                @trigger_error(sprintf('Setting the "%s" private service is deprecated since Symfony 3.2 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
+                @trigger_error(sprintf('The "%s" service is private, replacing it is deprecated since Symfony 3.2 and will fail in 4.0.', $id), E_USER_DEPRECATED);
             }
         } elseif ($wasSet && isset($this->methodMap[$id])) {
             if (null === $service) {
-                @trigger_error(sprintf('Unsetting the "%s" service after it\'s been initialized is deprecated since Symfony 3.3 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
+                @trigger_error(sprintf('The "%s" service is already initialized, unsetting it is deprecated since Symfony 3.3 and will fail in 4.0.', $id), E_USER_DEPRECATED);
             } else {
-                @trigger_error(sprintf('Setting the "%s" service after it\'s been initialized is deprecated since Symfony 3.3 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
+                @trigger_error(sprintf('The "%s" service is already initialized, replacing it is deprecated since Symfony 3.3 and will fail in 4.0.', $id), E_USER_DEPRECATED);
             }
         }
     }
@@ -224,7 +224,7 @@ class Container implements ResettableContainerInterface
     {
         for ($i = 2;;) {
             if (isset($this->privates[$id])) {
-                @trigger_error(sprintf('Checking for the existence of the "%s" private service is deprecated since Symfony 3.2 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
+                @trigger_error(sprintf('The "%s" service is private, checking for its existence is deprecated since Symfony 3.2 and will fail in 4.0.', $id), E_USER_DEPRECATED);
             }
             if (isset($this->aliases[$id])) {
                 $id = $this->aliases[$id];
@@ -282,7 +282,7 @@ class Container implements ResettableContainerInterface
         // calling $this->normalizeId($id) unless necessary.
         for ($i = 2;;) {
             if (isset($this->privates[$id])) {
-                @trigger_error(sprintf('Requesting the "%s" private service is deprecated since Symfony 3.2 and won\'t be supported anymore in Symfony 4.0.', $id), E_USER_DEPRECATED);
+                @trigger_error(sprintf('The "%s" service is private, getting it from the container is deprecated since Symfony 3.2 and will fail in 4.0. You should either make the service public, or stop getting services directly from the container and use dependency injection instead.', $id), E_USER_DEPRECATED);
             }
             if (isset($this->aliases[$id])) {
                 $id = $this->aliases[$id];
diff --git a/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php b/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
index 5cd988714a..3afc118b3d 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/ContainerTest.php
@@ -186,7 +186,7 @@ class ContainerTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Unsetting the "bar" service after it's been initialized is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation The "bar" service is already initialized, unsetting it is deprecated since Symfony 3.3 and will fail in 4.0.
      */
     public function testSetWithNullOnInitializedPredefinedService()
     {
@@ -452,7 +452,7 @@ class ContainerTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Unsetting the "internal" private service is deprecated since Symfony 3.2 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation The "internal" service is private, unsetting it is deprecated since Symfony 3.2 and will fail in 4.0.
      */
     public function testUnsetInternalPrivateServiceIsDeprecated()
     {
@@ -462,7 +462,7 @@ class ContainerTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Setting the "internal" private service is deprecated since Symfony 3.2 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation The "internal" service is private, replacing it is deprecated since Symfony 3.2 and will fail in 4.0.
      */
     public function testChangeInternalPrivateServiceIsDeprecated()
     {
@@ -473,7 +473,7 @@ class ContainerTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Checking for the existence of the "internal" private service is deprecated since Symfony 3.2 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation The "internal" service is private, checking for its existence is deprecated since Symfony 3.2 and will fail in 4.0.
      */
     public function testCheckExistenceOfAnInternalPrivateServiceIsDeprecated()
     {
@@ -484,7 +484,7 @@ class ContainerTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Requesting the "internal" private service is deprecated since Symfony 3.2 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation The "internal" service is private, getting it from the container is deprecated since Symfony 3.2 and will fail in 4.0. You should either make the service public, or stop getting services directly from the container and use dependency injection instead.
      */
     public function testRequestAnInternalSharedPrivateServiceIsDeprecated()
     {
@@ -495,7 +495,7 @@ class ContainerTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Setting the "bar" service after it's been initialized is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation The "bar" service is already initialized, replacing it is deprecated since Symfony 3.3 and will fail in 4.0.
      */
     public function testReplacingAPreDefinedServiceIsDeprecated()
     {
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php b/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
index d832a220c7..991337681f 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php
@@ -269,7 +269,7 @@ class PhpDumperTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Setting the "bar" service after it's been initialized is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation The "bar" service is already initialized, replacing it is deprecated since Symfony 3.3 and will fail in 4.0.
      */
     public function testOverrideServiceWhenUsingADumpedContainer()
     {
@@ -286,7 +286,7 @@ class PhpDumperTest extends TestCase
 
     /**
      * @group legacy
-     * @expectedDeprecation Setting the "bar" service after it's been initialized is deprecated since Symfony 3.3 and won't be supported anymore in Symfony 4.0.
+     * @expectedDeprecation The "bar" service is already initialized, replacing it is deprecated since Symfony 3.3 and will fail in 4.0.
      */
     public function testOverrideServiceWhenUsingADumpedContainerAndServiceIsUsedFromAnotherOne()
     {