diff --git a/include/aidge/backend/opencv/stimuli/StimuliImpl_opencv_imread.hpp b/include/aidge/backend/opencv/stimuli/StimuliImpl_opencv_imread.hpp
index 78590a16fc9236e06f8afd34bcf9735dae0314fd..49e983b04376b85d316ef624df439bdb335b6ba3 100644
--- a/include/aidge/backend/opencv/stimuli/StimuliImpl_opencv_imread.hpp
+++ b/include/aidge/backend/opencv/stimuli/StimuliImpl_opencv_imread.hpp
@@ -30,7 +30,7 @@
 namespace Aidge {
 class StimuliImpl_opencv_imread : public StimuliImpl {
 public:
-    StimuliImpl_opencv_imread(const std::string& dataPath="", int colorFlag=cv::IMREAD_COLOR) : 
+    StimuliImpl_opencv_imread(const std::string& dataPath="", int colorFlag=cv::IMREAD_UNCHANGED) : 
             mDataPath(dataPath),
             mColorFlag(colorFlag) {}
     virtual ~StimuliImpl_opencv_imread() {};
diff --git a/unit_tests/Test_Stimuli.cpp b/unit_tests/Test_Stimuli.cpp
index cf11584e9134adf1d64ba8ceae912ba529407756..48b0022b02a81653e62d0afbbc2350a4121e4b92 100644
--- a/unit_tests/Test_Stimuli.cpp
+++ b/unit_tests/Test_Stimuli.cpp
@@ -14,7 +14,7 @@ using namespace Aidge;
 TEST_CASE("Stimuli creation", "[Stimuli][OpenCV]") {
     SECTION("Instanciation & load an image") {
         //  Load image with imread
-        cv::Mat true_mat = cv::imread("/data1/is156025/tb256203/dev/eclipse_aidge/aidge/user_tests/train-images-idx3-ubyte[00001].pgm");
+        cv::Mat true_mat = cv::imread("/data1/is156025/tb256203/dev/eclipse_aidge/aidge/user_tests/train-images-idx3-ubyte[00001].pgm", cv::IMREAD_UNCHANGED);
         REQUIRE(true_mat.empty()==false);
 
         // Create Stimuli
diff --git a/unit_tests/Test_StimuliImpl_opencv_imread.cpp b/unit_tests/Test_StimuliImpl_opencv_imread.cpp
index ef3b048f31397cfb884bf5df603bf2558d905e51..2b19d997e53b7e6bd97211d3c9b2e4a72caf8e9d 100644
--- a/unit_tests/Test_StimuliImpl_opencv_imread.cpp
+++ b/unit_tests/Test_StimuliImpl_opencv_imread.cpp
@@ -15,7 +15,7 @@ TEST_CASE("StimuliImpl_opencv_imread creation", "[StimuliImpl_opencv_imread][Ope
     SECTION("Instanciation & load an image") {
         //  Load image with imread
         // cv::Mat true_mat = cv::imread("/data1/is156025/tb256203/dev/eclipse_aidge/aidge/user_tests/Lenna.png");
-        cv::Mat true_mat = cv::imread("/data1/is156025/tb256203/dev/eclipse_aidge/aidge/user_tests/train-images-idx3-ubyte[00001].pgm");
+        cv::Mat true_mat = cv::imread("/data1/is156025/tb256203/dev/eclipse_aidge/aidge/user_tests/train-images-idx3-ubyte[00001].pgm", cv::IMREAD_UNCHANGED);
         REQUIRE(true_mat.empty()==false);
 
         // Create StimuliImpl_opencv_imread