diff --git a/src/main/java/org/gcube/informationsystem/types/impl/properties/LinkedEntityImpl.java b/src/main/java/org/gcube/informationsystem/types/impl/properties/LinkedEntityImpl.java
index dc50bc5..dbecdc3 100644
--- a/src/main/java/org/gcube/informationsystem/types/impl/properties/LinkedEntityImpl.java
+++ b/src/main/java/org/gcube/informationsystem/types/impl/properties/LinkedEntityImpl.java
@@ -117,6 +117,11 @@ public final class LinkedEntityImpl extends PropertyElementImpl implements Linke
 			   Objects.equals(description, other.description);
 	}
 	
+	protected int compareIntegers(Integer thisInt, Integer otherInt) {
+		Integer thisInteger = thisInt == null ? Integer.MAX_VALUE : thisInt;
+		Integer otherInteger = otherInt == null ? Integer.MAX_VALUE : otherInt;
+		return thisInteger.compareTo(otherInteger);
+	}
 	
 	@Override
 	public int compareTo(LinkedEntity other) {
@@ -148,12 +153,12 @@ public final class LinkedEntityImpl extends PropertyElementImpl implements Linke
 			return ret;
 		}
 		
-		ret = max.compareTo(o.max);
+		ret = compareIntegers(max, o.max);
 		if(ret != 0) {
 			return ret;
 		}
 		
-		ret = min.compareTo(o.min);
+		ret = compareIntegers(min, o.min);
 		if(ret != 0) {
 			return ret;
 		}
diff --git a/src/main/java/org/gcube/informationsystem/types/impl/properties/PropertyDefinitionImpl.java b/src/main/java/org/gcube/informationsystem/types/impl/properties/PropertyDefinitionImpl.java
index 05be260..15e6e5c 100644
--- a/src/main/java/org/gcube/informationsystem/types/impl/properties/PropertyDefinitionImpl.java
+++ b/src/main/java/org/gcube/informationsystem/types/impl/properties/PropertyDefinitionImpl.java
@@ -206,6 +206,12 @@ public final class PropertyDefinitionImpl implements PropertyDefinition {
 				Objects.equals(propertyTypeName.toString(), other.propertyTypeName.toString());
 	}
 
+	protected int compareIntegers(Integer thisInt, Integer otherInt) {
+		Integer thisInteger = thisInt == null ? Integer.MAX_VALUE : thisInt;
+		Integer otherInteger = otherInt == null ? Integer.MAX_VALUE : otherInt;
+		return thisInteger.compareTo(otherInteger);
+	}
+	
 	@Override
 	public int compareTo(PropertyDefinition other) {
 		if (this == other) {
@@ -246,12 +252,12 @@ public final class PropertyDefinitionImpl implements PropertyDefinition {
 			return ret;
 		}
 		
-		ret = max.compareTo(o.max);
+		ret = compareIntegers(max, o.max);
 		if(ret != 0) {
 			return ret;
 		}
 		
-		ret = min.compareTo(o.min);
+		ret = compareIntegers(min, o.min);
 		if(ret != 0) {
 			return ret;
 		}