diff --git a/modules/line_descriptor/samples/knn_matching.cpp b/modules/line_descriptor/samples/knn_matching.cpp
index 361813308..a59b6caba 100644
--- a/modules/line_descriptor/samples/knn_matching.cpp
+++ b/modules/line_descriptor/samples/knn_matching.cpp
@@ -111,7 +111,7 @@ uchar invertSingleBits( uchar dividend_char, int numBits )
   /* reconvert to decimal */
   uchar result = 0;
   for ( int i = (int) bin_vector.size() - 1; i >= 0; i-- )
-    result += (uchar) ( bin_vector[i] * pow( 2, i ) );
+    result += (uchar) ( bin_vector[i] * (1 << i) );
 
   return result;
 }
diff --git a/modules/optflow/samples/optical_flow_evaluation.cpp b/modules/optflow/samples/optical_flow_evaluation.cpp
index 4ecc798d5..4891d13cc 100644
--- a/modules/optflow/samples/optical_flow_evaluation.cpp
+++ b/modules/optflow/samples/optical_flow_evaluation.cpp
@@ -2,6 +2,7 @@
 #include "opencv2/video.hpp"
 #include "opencv2/optflow.hpp"
 #include <fstream>
+#include <limits>
 
 using namespace std;
 using namespace cv;
@@ -40,7 +41,7 @@ static Mat endpointError( const Mat_<Point2f>& flow1, const Mat_<Point2f>& flow2
                 const Point2f diff = u1 - u2;
                 result.at<float>(i, j) = sqrt((float)diff.ddot(diff)); //distance
             } else
-                result.at<float>(i, j) = NAN;
+                result.at<float>(i, j) = std::numeric_limits<float>::quiet_NaN();
         }
     }
     return result;
@@ -61,7 +62,7 @@ static Mat angularError( const Mat_<Point2f>& flow1, const Mat_<Point2f>& flow2
             if ( isFlowCorrect(u1) && isFlowCorrect(u2) )
                 result.at<float>(i, j) = acos((float)(u1.ddot(u2) / norm(u1) * norm(u2)));
             else
-                result.at<float>(i, j) = NAN;
+                result.at<float>(i, j) = std::numeric_limits<float>::quiet_NaN();
         }
     }
     return result;