diff --git a/modules/calib3d/src/usac/ransac_solvers.cpp b/modules/calib3d/src/usac/ransac_solvers.cpp
index 65fa2d3b9f..0c7637d582 100644
--- a/modules/calib3d/src/usac/ransac_solvers.cpp
+++ b/modules/calib3d/src/usac/ransac_solvers.cpp
@@ -286,7 +286,7 @@ public:
                             current_score = quality->getScore(models[i]);
                         } else {
                             if (is_magsac && iters % repeat_magsac == 0) {
-                                if (!local_optimization->refineModel
+                                if (local_optimization && !local_optimization->refineModel
                                         (models[i], best_score_thread, models[i], current_score))
                                     continue;
                             } else if (model_verifier->isModelGood(models[i])) {
@@ -1028,4 +1028,4 @@ bool run (const Ptr<const Model> &params, InputArray points1, InputArray points2
     }
     return false;
 }
-}}
\ No newline at end of file
+}}
diff --git a/modules/core/src/dxt.cpp b/modules/core/src/dxt.cpp
index b307703a32..fcdb2a202f 100644
--- a/modules/core/src/dxt.cpp
+++ b/modules/core/src/dxt.cpp
@@ -531,14 +531,14 @@ template<typename T> struct DFT_R5
 template<typename T> struct DFT_VecR2
 {
     void operator()(Complex<T>* dst, const int c_n, const int n, const int dw0, const Complex<T>* wave) const {
-        return DFT_R2<T>()(dst, c_n, n, dw0, wave);
+        DFT_R2<T>()(dst, c_n, n, dw0, wave);
     }
 };
 
 template<typename T> struct DFT_VecR3
 {
     void operator()(Complex<T>* dst, const int c_n, const int n, const int dw0, const Complex<T>* wave) const {
-        return DFT_R3<T>()(dst, c_n, n, dw0, wave);
+        DFT_R3<T>()(dst, c_n, n, dw0, wave);
     }
 };
 
diff --git a/modules/gapi/include/opencv2/gapi/render/render_types.hpp b/modules/gapi/include/opencv2/gapi/render/render_types.hpp
index 08b14d1ddd..ca403be361 100644
--- a/modules/gapi/include/opencv2/gapi/render/render_types.hpp
+++ b/modules/gapi/include/opencv2/gapi/render/render_types.hpp
@@ -252,7 +252,7 @@ struct Mosaic
     {
     }
 
-    Mosaic() = default;
+    Mosaic() : cellSz(0), decim(0) {}
 
     /*@{*/
     cv::Rect   mos;    //!< Coordinates of the mosaic
diff --git a/modules/objdetect/src/qrcode.cpp b/modules/objdetect/src/qrcode.cpp
index c42bb8a309..d47f1d3a20 100644
--- a/modules/objdetect/src/qrcode.cpp
+++ b/modules/objdetect/src/qrcode.cpp
@@ -1122,7 +1122,7 @@ bool QRDecode::computeClosestPoints(const vector<Point> &result_integer_hull)
 {
     CV_TRACE_FUNCTION();
     double min_norm, max_norm = 0.0;
-    size_t idx_min;
+    size_t idx_min = (size_t)-1;
     for (size_t i = 0; i < original_points.size(); i++)
     {
         min_norm = std::numeric_limits<double>::max();
@@ -1144,6 +1144,7 @@ bool QRDecode::computeClosestPoints(const vector<Point> &result_integer_hull)
             max_norm = min_norm;
             unstable_pair = std::pair<size_t,Point>(i, closest_pnt);
         }
+        CV_Assert(idx_min != (size_t)-1);
         closest_points.push_back(std::pair<size_t,Point>(idx_min, closest_pnt));
     }