diff --git a/src/main/java/org/orekit/rugged/adjustment/OptimizationProblemBuilder.java b/src/main/java/org/orekit/rugged/adjustment/OptimizationProblemBuilder.java
index 990172adca948888b3681b64f5f8d167c0032702..db1d23969d11fe96beda99c155c76d8beb42e622 100644
--- a/src/main/java/org/orekit/rugged/adjustment/OptimizationProblemBuilder.java
+++ b/src/main/java/org/orekit/rugged/adjustment/OptimizationProblemBuilder.java
@@ -110,6 +110,16 @@ abstract class OptimizationProblemBuilder {
     }
 
 
+    /**
+     * generator getter.
+     *
+     * @return the derivative structure generator.
+     */
+    public final DSGenerator getGenerator() {
+        return this.generator;
+    }
+
+
 
     /** leastsquare problem builder.
      * @param maxEvaluations maxIterations and evaluations