diff --git a/api/server/src/main/java/org/softwareheritage/graph/SwhId.java b/api/server/src/main/java/org/softwareheritage/graph/SwhId.java
index b413291..49dab71 100644
--- a/api/server/src/main/java/org/softwareheritage/graph/SwhId.java
+++ b/api/server/src/main/java/org/softwareheritage/graph/SwhId.java
@@ -1,59 +1,59 @@
 package org.softwareheritage.graph;
 
 import com.fasterxml.jackson.annotation.JsonValue;
 
 public class SwhId {
   public static final int HASH_LENGTH = 40;
 
   String swhId;
   String type;
   String hash;
 
   // SWH ID format: 'swh:1:type:hash'
   // https://docs.softwareheritage.org/devel/swh-model/persistent-identifiers.html
   public SwhId(String swhId) {
     this.swhId = swhId;
 
     String[] parts = swhId.split(":");
     if (parts.length != 4 || !parts[0].equals("swh") || !parts[1].equals("1")) {
       throw new IllegalArgumentException("Expected SWH ID format to be 'swh:1:type:hash', got: " + swhId);
     }
 
     this.type = parts[2];
     if (!type.matches("cnt|dir|rel|rev|snp")) {
       throw new IllegalArgumentException("Unknown SWH ID type in: " + swhId);
     }
 
     this.hash = parts[3];
     if (!hash.matches("[0-9a-f]{" + HASH_LENGTH + "}")) {
-      throw new IllegalArgumentException("Unknown SWH ID hash in: " + swhId);
+      throw new IllegalArgumentException("Wrong SWH ID hash format in: " + swhId);
     }
   }
 
   @Override
   public boolean equals(Object otherObj) {
     if (otherObj == this) return true;
     if (!(otherObj instanceof SwhId)) return false;
 
     SwhId other = (SwhId) otherObj;
     return swhId.equals(other.getSwhId());
   }
 
   @Override
   public String toString() {
     return swhId;
   }
 
   @JsonValue
   public String getSwhId() {
     return swhId;
   }
 
   public String getType() {
     return type;
   }
 
   public String getHash() {
     return hash;
   }
 }