diff --git a/src/main/java/dev/dnpm/etl/processor/pseudonym/GpasPseudonymGenerator.java b/src/main/java/dev/dnpm/etl/processor/pseudonym/GpasPseudonymGenerator.java
index 732a770..91e465b 100644
--- a/src/main/java/dev/dnpm/etl/processor/pseudonym/GpasPseudonymGenerator.java
+++ b/src/main/java/dev/dnpm/etl/processor/pseudonym/GpasPseudonymGenerator.java
@@ -108,12 +108,19 @@ public class GpasPseudonymGenerator implements Generator {
 
     @NotNull
     public static String unwrapPseudonym(Parameters gPasPseudonymResult) {
-        Identifier pseudonym = (Identifier) gPasPseudonymResult.getParameter().stream().findFirst()
-            .get().getPart().stream().filter(a -> a.getName().equals("pseudonym")).findFirst()
-            .orElseGet(ParametersParameterComponent::new).getValue();
+        final var parameters = gPasPseudonymResult.getParameter().stream().findFirst();
+
+        if (parameters.isEmpty()) {
+            throw new PseudonymRequestFailed("Empty HL7 parameters, cannot find first one");
+        }
+
+        final var identifier = (Identifier) parameters.get().getPart().stream()
+                .filter(a -> a.getName().equals("pseudonym"))
+                .findFirst()
+                .orElseGet(ParametersParameterComponent::new).getValue();
 
         // pseudonym
-        return pseudonym.getSystem() + "|" + pseudonym.getValue();
+        return identifier.getSystem() + "|" + identifier.getValue();
     }