diff --git a/modules/calib3d/src/ippe.cpp b/modules/calib3d/src/ippe.cpp
index ec6089596c..c3d2744469 100644
--- a/modules/calib3d/src/ippe.cpp
+++ b/modules/calib3d/src/ippe.cpp
@@ -303,13 +303,17 @@ void PoseSolver::rot2vec(InputArray _R, OutputArray _r)
     Mat rvec = _r.getMat();
 
     double trace = R.at<double>(0, 0) + R.at<double>(1, 1) + R.at<double>(2, 2);
-    double w_norm = acos((trace - 1.0) / 2.0);
+    double w_norm = acos(std::min(std::max((trace - 1.0) / 2.0, -1.0), 1.0));
     double eps = std::numeric_limits<float>::epsilon();
     double d = 1 / (2 * sin(w_norm)) * w_norm;
     if (w_norm < eps) //rotation is the identity
     {
         rvec.setTo(0);
     }
+    else if (sin(w_norm) < 1e-5) //close to 180 degrees, the axis can't be read from R - R^T
+    {
+        Rodrigues(R, rvec);
+    }
     else
     {
         double c0 = R.at<double>(2, 1) - R.at<double>(1, 2);
diff --git a/modules/calib3d/test/test_solvepnp_ransac.cpp b/modules/calib3d/test/test_solvepnp_ransac.cpp
index 3cbb0d2ccf..a13468979d 100644
--- a/modules/calib3d/test/test_solvepnp_ransac.cpp
+++ b/modules/calib3d/test/test_solvepnp_ransac.cpp
@@ -2404,4 +2404,30 @@ TEST(AP3P, ctheta1p_nan_23607)
     }
 }
 
+TEST(Calib3d_SolvePnP, regression_30402)
+{
+    // A tag seen exactly head-on: the pose has a 180 degree rotation about X.
+    const double L = 0.05;
+    std::vector<Point3d> objectPoints = {
+        Point3d(-L,  L, 0), Point3d( L,  L, 0), Point3d( L, -L, 0), Point3d(-L, -L, 0)
+    };
+    Matx33d intrinsics(800, 0, 320,
+                       0, 800, 240,
+                       0, 0, 1);
+    Vec3d rvecGT(CV_PI, 0, 0), tvecGT(0, 0, 0.5);
+
+    std::vector<Point2d> imagePoints;
+    projectPoints(objectPoints, rvecGT, tvecGT, intrinsics, noArray(), imagePoints);
+
+    Mat rvec, tvec;
+    ASSERT_TRUE(solvePnP(objectPoints, imagePoints, intrinsics, noArray(), rvec, tvec,
+                         false, SOLVEPNP_IPPE_SQUARE));
+
+    Mat R, RGT;
+    cv::Rodrigues(rvec, R);
+    cv::Rodrigues(rvecGT, RGT);
+    EXPECT_LE(cvtest::norm(R, RGT, NORM_INF), 1e-6);
+    EXPECT_LE(cvtest::norm(tvec, Mat(tvecGT), NORM_INF), 1e-6);
+}
+
 }} // namespace