diff --git a/gtsam/linear/linearExceptions.h b/gtsam/linear/linearExceptions.h
index 4afc4f67e..62f12cc2e 100644
--- a/gtsam/linear/linearExceptions.h
+++ b/gtsam/linear/linearExceptions.h
@@ -95,7 +95,7 @@ namespace gtsam {
   class GTSAM_EXPORT IndeterminantLinearSystemException : public ThreadsafeException<IndeterminantLinearSystemException> {
     Index j_;
   public:
-    IndeterminantLinearSystemException(Index j) throw();
+    IndeterminantLinearSystemException(Index j) throw() : j_(j) {}
     virtual ~IndeterminantLinearSystemException() throw() {}
     Index nearbyVariable() const { return j_; }
     virtual const char* what() const throw();