diff --git a/pgjdbc/src/main/java/org/postgresql/util/PSQLState.java b/pgjdbc/src/main/java/org/postgresql/util/PSQLState.java
index fb67a4fff4..0ca4a602dd 100644
--- a/pgjdbc/src/main/java/org/postgresql/util/PSQLState.java
+++ b/pgjdbc/src/main/java/org/postgresql/util/PSQLState.java
@@ -59,6 +59,8 @@ public enum PSQLState {
   MOST_SPECIFIC_TYPE_DOES_NOT_MATCH("2200G"),
   INVALID_PARAMETER_VALUE("22023"),
 
+  UNIQUE_CONSTRAINT_VIOLATION("23505"),
+
   INVALID_CURSOR_STATE("24000"),
 
   TRANSACTION_STATE_INVALID("25000"),