diff --git a/org.eclipse.xtext.testlanguages.ide/.classpath b/org.eclipse.xtext.testlanguages.ide/.classpath
index 6a2f07cbc..b07546782 100644
--- a/org.eclipse.xtext.testlanguages.ide/.classpath
+++ b/org.eclipse.xtext.testlanguages.ide/.classpath
@@ -7,6 +7,7 @@
 	</classpathentry>
 	<classpathentry kind="src" path="src-gen">
 		<attributes>
+			<attribute name="ignore_optional_problems" value="true"/>
 			<attribute name="FROM_GRADLE_MODEL" value="true"/>
 		</attributes>
 	</classpathentry>
diff --git a/org.eclipse.xtext.testlanguages/.classpath b/org.eclipse.xtext.testlanguages/.classpath
index 5b4213581..614b28f8a 100644
--- a/org.eclipse.xtext.testlanguages/.classpath
+++ b/org.eclipse.xtext.testlanguages/.classpath
@@ -12,6 +12,7 @@
 	</classpathentry>
 	<classpathentry kind="src" path="src-gen">
 		<attributes>
+			<attribute name="ignore_optional_problems" value="true"/>
 			<attribute name="FROM_GRADLE_MODEL" value="true"/>
 		</attributes>
 	</classpathentry>
diff --git a/org.eclipse.xtext.tests/.classpath b/org.eclipse.xtext.tests/.classpath
index a1eedd561..6a1fbd8f3 100644
--- a/org.eclipse.xtext.tests/.classpath
+++ b/org.eclipse.xtext.tests/.classpath
@@ -12,11 +12,13 @@
 	</classpathentry>
 	<classpathentry kind="src" path="src-gen">
 		<attributes>
+			<attribute name="ignore_optional_problems" value="true"/>
 			<attribute name="FROM_GRADLE_MODEL" value="true"/>
 		</attributes>
 	</classpathentry>
 	<classpathentry kind="src" path="emf-gen">
 		<attributes>
+			<attribute name="ignore_optional_problems" value="true"/>
 			<attribute name="FROM_GRADLE_MODEL" value="true"/>
 		</attributes>
 	</classpathentry>
diff --git a/org.eclipse.xtext.xtext.generator/.classpath b/org.eclipse.xtext.xtext.generator/.classpath
index 5b4213581..614b28f8a 100644
--- a/org.eclipse.xtext.xtext.generator/.classpath
+++ b/org.eclipse.xtext.xtext.generator/.classpath
@@ -12,6 +12,7 @@
 	</classpathentry>
 	<classpathentry kind="src" path="src-gen">
 		<attributes>
+			<attribute name="ignore_optional_problems" value="true"/>
 			<attribute name="FROM_GRADLE_MODEL" value="true"/>
 		</attributes>
 	</classpathentry>
diff --git a/org.eclipse.xtext/.classpath b/org.eclipse.xtext/.classpath
index 2a152fac3..86691cd4d 100644
--- a/org.eclipse.xtext/.classpath
+++ b/org.eclipse.xtext/.classpath
@@ -12,11 +12,13 @@
 	</classpathentry>
 	<classpathentry kind="src" path="src-gen">
 		<attributes>
+			<attribute name="ignore_optional_problems" value="true"/>
 			<attribute name="FROM_GRADLE_MODEL" value="true"/>
 		</attributes>
 	</classpathentry>
 	<classpathentry kind="src" path="emf-gen">
 		<attributes>
+			<attribute name="ignore_optional_problems" value="true"/>
 			<attribute name="FROM_GRADLE_MODEL" value="true"/>
 		</attributes>
 	</classpathentry>