diff --git a/tmva/sofie/test/TestCustomModelsFromONNX.cxx b/tmva/sofie/test/TestCustomModelsFromONNX.cxx
index 94993f601a3c4..07bc0d7480d87 100644
--- a/tmva/sofie/test/TestCustomModelsFromONNX.cxx
+++ b/tmva/sofie/test/TestCustomModelsFromONNX.cxx
@@ -918,6 +918,21 @@ TEST(ONNX, Pow_broadcast){
 
 }
 
+TEST(ONNX, ReduceMean_kFirst)
+{
+   // ReduceMean over axis=0 (kFirst path) on a [3,4] tensor.
+   std::vector<float> input(12);
+   std::iota(input.begin(), input.end(), 0.0f);
+   std::vector<float> correct_output = {4, 5, 6, 7};
+
+   ASSERT_INCLUDE_AND_RUN(std::vector<float>, "ReduceMean_kFirst", input);
+
+   EXPECT_EQ(output.size(), correct_output.size());
+   for (size_t i = 0; i < output.size(); ++i) {
+      EXPECT_LE(std::abs(output[i] - correct_output[i]), DEFAULT_TOLERANCE);
+   }
+}
+
    TEST(ONNX, ReduceProd){
    constexpr float TOLERANCE = DEFAULT_TOLERANCE;
 
diff --git a/tmva/sofie/test/input_models/ReduceMean_kFirst.onnx b/tmva/sofie/test/input_models/ReduceMean_kFirst.onnx
new file mode 100644
index 0000000000000..7d5e7bad145f6
Binary files /dev/null and b/tmva/sofie/test/input_models/ReduceMean_kFirst.onnx differ