diff --git a/internal/ceres/program.h b/internal/ceres/program.h
index 5002b7e..4288f60 100644
--- a/internal/ceres/program.h
+++ b/internal/ceres/program.h
@@ -99,6 +99,10 @@
   // position of the parameter in the state and delta vector respectively.
   void SetParameterOffsetsAndIndex();
 
+  // Check if the internal state of the program (the indexing and the
+  // offsets) are correct.
+  bool IsValid() const;
+
   // See problem.h for what these do.
   int NumParameterBlocks() const;
   int NumParameters() const;