diff --git a/model/certification-impl/src/main/java/com/evolveum/midpoint/certification/impl/AccCertReviewersHelper.java b/model/certification-impl/src/main/java/com/evolveum/midpoint/certification/impl/AccCertReviewersHelper.java
index b1ddb2288f8..47bbba89548 100644
--- a/model/certification-impl/src/main/java/com/evolveum/midpoint/certification/impl/AccCertReviewersHelper.java
+++ b/model/certification-impl/src/main/java/com/evolveum/midpoint/certification/impl/AccCertReviewersHelper.java
@@ -93,7 +93,8 @@ List<ObjectReferenceType> getReviewersForCase(AccessCertificationCaseType _case,
         }
         for (ExpressionType reviewerExpression : reviewerSpec.getReviewerExpression()) {
 			ExpressionVariables variables = new ExpressionVariables();
-			variables.put(ExpressionConstants.VAR_CERTIFICATION_CASE, _case, _case.asPrismContainerValue().getDefinition());
+			// The _case does NOT have definition here. Can we have it?
+			variables.put(ExpressionConstants.VAR_CERTIFICATION_CASE, _case, AccessCertificationCaseType.class);
 			variables.putObject(ExpressionConstants.VAR_CAMPAIGN, campaign, AccessCertificationCampaignType.class);
 			variables.put(ExpressionConstants.VAR_REVIEWER_SPECIFICATION, reviewerSpec, AccessCertificationReviewerSpecificationType.class);
 			List<ObjectReferenceType> refList = expressionHelper
diff --git a/repo/repo-common/src/main/java/com/evolveum/midpoint/repo/common/expression/ExpressionUtil.java b/repo/repo-common/src/main/java/com/evolveum/midpoint/repo/common/expression/ExpressionUtil.java
index e21cb4a4e6e..f32d618fae0 100644
--- a/repo/repo-common/src/main/java/com/evolveum/midpoint/repo/common/expression/ExpressionUtil.java
+++ b/repo/repo-common/src/main/java/com/evolveum/midpoint/repo/common/expression/ExpressionUtil.java
@@ -73,6 +73,7 @@
 import com.evolveum.midpoint.prism.query.TypeFilter;
 import com.evolveum.midpoint.prism.query.UndefinedFilter;
 import com.evolveum.midpoint.prism.query.ValueFilter;
+import com.evolveum.midpoint.prism.util.DefinitionResolver;
 import com.evolveum.midpoint.prism.util.ItemDeltaItem;
 import com.evolveum.midpoint.prism.util.JavaTypeConverter;
 import com.evolveum.midpoint.prism.util.ObjectDeltaObject;
@@ -349,7 +350,19 @@ private static  <T> TypedValue<T> determineTypedValue(PrismContext prismContext,
 	
 	private static  <T,O extends ObjectType> TypedValue<T> determineTypedValueOdo(PrismContext prismContext, String name, TypedValue<O> root, ItemPath relativePath) throws SchemaException {
 		ObjectDeltaObject<O> rootOdo = (ObjectDeltaObject<O>) root.getValue();
-		ItemDeltaItem<PrismValue, ItemDefinition> subValue = rootOdo.findIdi(relativePath);
+		DefinitionResolver<PrismObjectDefinition<O>, ItemDefinition> resolver = (rootDef,path) -> {
+			// We are called just before failure. Therefore all normal ways of resolving of definition did not work.
+			ItemDefinition parentDef = rootDef.findItemDefinition(path.allExceptLast());
+			if (parentDef != null && parentDef.isDynamic()) {
+				// This is the case of dynamic schema extensions, such as assignment extension.
+    			// Those may not have a definition. In that case just assume strings.
+    			// In fact, this is a HACK. All such schemas should have a definition.
+    			// Otherwise there may be problems with parameter types for caching compiles scripts and so on.
+    			return prismContext.definitionFactory().createPropertyDefinition(path.firstName(), PrimitiveType.STRING.getQname());
+			}
+			return null;
+		};
+		ItemDeltaItem<PrismValue, ItemDefinition> subValue = rootOdo.findIdi(relativePath, resolver);
 		PrismObjectDefinition<O> rootDefinition = root.getDefinition();
 		if (rootDefinition == null) {
 			rootDefinition = rootOdo.getDefinition();