diff --git a/modules/calib3d/src/fisheye.cpp b/modules/calib3d/src/fisheye.cpp
index 0a8db58d83..32dc15c3f2 100644
--- a/modules/calib3d/src/fisheye.cpp
+++ b/modules/calib3d/src/fisheye.cpp
@@ -1040,8 +1040,10 @@ double cv::fisheye::stereoCalibrate(InputArrayOfArrays objectPoints, InputArrayO
         int b = cv::countNonZero(intrinsicRight.isEstimate);
         cv::Mat deltas;
         solve(J.t() * J, J.t()*e, deltas);
-        intrinsicLeft = intrinsicLeft + deltas.rowRange(0, a);
-        intrinsicRight = intrinsicRight + deltas.rowRange(a, a + b);
+        if (a > 0)
+            intrinsicLeft = intrinsicLeft + deltas.rowRange(0, a);
+        if (b > 0)
+            intrinsicRight = intrinsicRight + deltas.rowRange(a, a + b);
         omcur = omcur + cv::Vec3d(deltas.rowRange(a + b, a + b + 3));
         Tcur = Tcur + cv::Vec3d(deltas.rowRange(a + b + 3, a + b + 6));
         for (int image_idx = 0; image_idx < n_images; ++image_idx)
diff --git a/modules/core/include/opencv2/core/mat.inl.hpp b/modules/core/include/opencv2/core/mat.inl.hpp
index 178db1b882..31638afd01 100644
--- a/modules/core/include/opencv2/core/mat.inl.hpp
+++ b/modules/core/include/opencv2/core/mat.inl.hpp
@@ -689,6 +689,16 @@ void Mat::release()
     datastart = dataend = datalimit = data = 0;
     for(int i = 0; i < dims; i++)
         size.p[i] = 0;
+#ifdef _DEBUG
+    flags = MAGIC_VAL;
+    dims = rows = cols = 0;
+    if(step.p != step.buf)
+    {
+        fastFree(step.p);
+        step.p = step.buf;
+        size.p = &rows;
+    }
+#endif
 }
 
 inline
diff --git a/modules/core/misc/java/test/MatTest.java b/modules/core/misc/java/test/MatTest.java
index a2570f4342..3ff0c8be07 100644
--- a/modules/core/misc/java/test/MatTest.java
+++ b/modules/core/misc/java/test/MatTest.java
@@ -494,7 +494,7 @@ public class MatTest extends OpenCVTestCase {
 
     public void testIsSubmatrix() {
         assertFalse(gray0.isSubmatrix());
-        Mat subMat = gray0.submat(0, 0, gray0.rows() / 2, gray0.cols() / 2);
+        Mat subMat = gray0.submat(0, gray0.rows() / 2, 0, gray0.cols() / 2);
         assertTrue(subMat.isSubmatrix());
     }