diff --git a/gtsam/nonlinear/NonlinearFactorGraph.cpp b/gtsam/nonlinear/NonlinearFactorGraph.cpp
index 0d1ed3148..0e0d70268 100644
--- a/gtsam/nonlinear/NonlinearFactorGraph.cpp
+++ b/gtsam/nonlinear/NonlinearFactorGraph.cpp
@@ -54,9 +54,14 @@ void NonlinearFactorGraph::print(const std::string& str, const KeyFormatter& key
   for (size_t i = 0; i < factors_.size(); i++) {
     stringstream ss;
     ss << "Factor " << i << ": ";
-    if (factors_[i] != nullptr) factors_[i]->print(ss.str(), keyFormatter);
-    cout << endl;
+    if (factors_[i] != nullptr) {
+      factors_[i]->print(ss.str(), keyFormatter);
+      cout << "\n";
+    } else {
+      cout << ss.str() << "nullptr\n";
+    }
   }
+  std::cout.flush();
 }
 
 /* ************************************************************************* */
@@ -80,8 +85,9 @@ void NonlinearFactorGraph::printErrors(const Values& values, const std::string&
       factor->print(ss.str(), keyFormatter);
       cout << "error = " << errorValue << "\n";
     }
-    cout << endl; // only one "endl" at end might be faster, \n for each factor
+    cout << "\n";
   }
+  std::cout.flush();
 }
 
 /* ************************************************************************* */