diff --git a/c_src/esqlite3_nif.c b/c_src/esqlite3_nif.c
index b9d8784..5861bb1 100644
--- a/c_src/esqlite3_nif.c
+++ b/c_src/esqlite3_nif.c
@@ -508,6 +508,8 @@ do_step(ErlNifEnv *env, sqlite3 *db, sqlite3_stmt *stmt)
         return make_sqlite3_error_tuple(env, rc, db);
     if(rc == SQLITE_MISUSE)
         return make_error_tuple(env, "misuse");
+    if(rc == SQLITE_CONSTRAINT)
+        return make_sqlite3_error_tuple(env, rc, db);
 
     return make_error_tuple(env, "unexpected_return_value");
 }