diff --git a/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/asapi/v3/executor/material/CreateMaterialTypesOperationExecutor.java b/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/asapi/v3/executor/material/CreateMaterialTypesOperationExecutor.java
index a09e6037c4755f76ed324b7f472fa387017d9a9d..9194dfa09fafb848e9053b24932e11016f08a477 100644
--- a/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/asapi/v3/executor/material/CreateMaterialTypesOperationExecutor.java
+++ b/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/asapi/v3/executor/material/CreateMaterialTypesOperationExecutor.java
@@ -90,7 +90,7 @@ public class CreateMaterialTypesOperationExecutor
                     PropertyTypePE type =
                             findPropertyType(context,
                                     propertyAssignmentCreation.getPropertyTypeId());
-                    if (type.getType() != null && INVALID_TYPES.contains(type.getType().getCode()))
+                    if (type != null && type.getType() != null && INVALID_TYPES.contains(type.getType().getCode()))
                     {
                         return false;
                     }
@@ -106,11 +106,6 @@ public class CreateMaterialTypesOperationExecutor
         Map<IPropertyTypeId, PropertyTypePE> propertyTypePEMap =
                 mapPropertyTypeByIdExecutor.map(context, Arrays.asList(propertyTypeId));
         PropertyTypePE propertyTypePE = propertyTypePEMap.get(propertyTypeId);
-
-        if (propertyTypePE == null)
-        {
-            throw new ObjectNotFoundException(propertyTypeId);
-        }
         return propertyTypePE;
     }
 
diff --git a/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/asapi/v3/executor/material/UpdateMaterialTypesOperationExecutor.java b/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/asapi/v3/executor/material/UpdateMaterialTypesOperationExecutor.java
index de0dbb2a168bafcd3a2a12af0328ed16994d8c1e..f947c0ebafc4cdf0017f68bad4d96a90866d0ee1 100644
--- a/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/asapi/v3/executor/material/UpdateMaterialTypesOperationExecutor.java
+++ b/server-application-server/source/java/ch/ethz/sis/openbis/generic/server/asapi/v3/executor/material/UpdateMaterialTypesOperationExecutor.java
@@ -92,7 +92,7 @@ public class UpdateMaterialTypesOperationExecutor
                     {
                         PropertyTypePE type =
                                 findPropertyType(context, addedAssignments.getPropertyTypeId());
-                        if (type.getType() != null && INVALID_TYPES.contains(
+                        if (type != null && type.getType() != null && INVALID_TYPES.contains(
                                 type.getType().getCode()))
                         {
                             return false;
@@ -106,7 +106,7 @@ public class UpdateMaterialTypesOperationExecutor
                     {
                         PropertyTypePE type =
                                 findPropertyType(context, setAssignments.getPropertyTypeId());
-                        if (type.getType() != null && INVALID_TYPES.contains(
+                        if (type != null && type.getType() != null && INVALID_TYPES.contains(
                                 type.getType().getCode()))
                         {
                             return false;
@@ -124,11 +124,6 @@ public class UpdateMaterialTypesOperationExecutor
         Map<IPropertyTypeId, PropertyTypePE> propertyTypePEMap =
                 mapPropertyTypeByIdExecutor.map(context, Arrays.asList(propertyTypeId));
         PropertyTypePE propertyTypePE = propertyTypePEMap.get(propertyTypeId);
-
-        if (propertyTypePE == null)
-        {
-            throw new ObjectNotFoundException(propertyTypeId);
-        }
         return propertyTypePE;
     }