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 7b631d8..07f16c5 100644
--- a/src/main/java/dev/dnpm/etl/processor/pseudonym/GpasPseudonymGenerator.java
+++ b/src/main/java/dev/dnpm/etl/processor/pseudonym/GpasPseudonymGenerator.java
@@ -127,7 +127,21 @@ public class GpasPseudonymGenerator implements Generator {
             .orElseGet(ParametersParameterComponent::new).getValue();
 
         // pseudonym
-        return identifier.getSystem() + "|" + identifier.getValue();
+        return sanitizeValue(identifier.getValue());
+    }
+
+    /**
+     * Allow only filename friendly values
+     *
+     * @param psnValue GAPS pseudonym value
+     * @return cleaned up value
+     */
+    public static String sanitizeValue(String psnValue) {
+        // pattern to match forbidden characters
+        String forbiddenCharsRegex = "[\\\\/:*?\"<>|;]";
+
+        // Replace all forbidden characters with underscores
+        return psnValue.replaceAll(forbiddenCharsRegex, "_");
     }
 
 
diff --git a/src/test/kotlin/dev/dnpm/etl/processor/pseudonym/PseudonymizeServiceTest.kt b/src/test/kotlin/dev/dnpm/etl/processor/pseudonym/PseudonymizeServiceTest.kt
index a30a328..4646ff6 100644
--- a/src/test/kotlin/dev/dnpm/etl/processor/pseudonym/PseudonymizeServiceTest.kt
+++ b/src/test/kotlin/dev/dnpm/etl/processor/pseudonym/PseudonymizeServiceTest.kt
@@ -70,6 +70,13 @@ class PseudonymizeServiceTest {
         assertThat(mtbFile.patient.id).isEqualTo("123")
     }
 
+    @Test
+    fun sanitizeFileName(@Mock generator: GpasPseudonymGenerator) {
+        val result= GpasPseudonymGenerator.sanitizeValue("l://a\\bs;1*2?3>")
+
+        assertThat(result).isEqualTo("l___a_bs_1_2_3_")
+    }
+
     @Test
     fun shouldUsePseudonymPrefixForBuiltin(@Mock generator: AnonymizingGenerator) {
         doAnswer {