diff --git a/examples/heif_enc.cc b/examples/heif_enc.cc
index a62f878d18..f98a379138 100644
--- a/examples/heif_enc.cc
+++ b/examples/heif_enc.cc
@@ -64,9 +64,9 @@ int metadata_compression = 0;
 const char* encoderId = nullptr;
 std::string chroma_downsampling;
 
-uint16_t nclx_matrix_coefficients = 1;
 uint16_t nclx_colour_primaries = 1;
 uint16_t nclx_transfer_characteristic = 13;
+uint16_t nclx_matrix_coefficients = 5;
 int nclx_full_range = true;
 
 std::string property_pitm_description;
diff --git a/libheif/color-conversion/colorconversion.cc b/libheif/color-conversion/colorconversion.cc
index 3a7b35315b..5a0d6b57a4 100644
--- a/libheif/color-conversion/colorconversion.cc
+++ b/libheif/color-conversion/colorconversion.cc
@@ -520,7 +520,7 @@ std::shared_ptr<HeifPixelImage> convert_colorspace(const std::shared_ptr<HeifPix
     input_state.nclx_profile = *input->get_color_profile_nclx();
   }
 
-  input_state.nclx_profile.replace_undefined_values_with_defaults();
+  input_state.nclx_profile.replace_undefined_values_with_sRGB_defaults();
 
   std::set<enum heif_channel> channels = input->get_channel_set();
   assert(!channels.empty());
diff --git a/libheif/context.cc b/libheif/context.cc
index ec850c8e74..c7e49ea538 100644
--- a/libheif/context.cc
+++ b/libheif/context.cc
@@ -2446,7 +2446,7 @@ static std::shared_ptr<color_profile_nclx> compute_target_nclx_profile(const std
     target_nclx_profile->set_undefined();
   }
 
-  target_nclx_profile->replace_undefined_values_with_defaults();
+  target_nclx_profile->replace_undefined_values_with_sRGB_defaults();
 
   return target_nclx_profile;
 }
diff --git a/libheif/nclx.cc b/libheif/nclx.cc
index ded33d8fe2..3be972d7ca 100644
--- a/libheif/nclx.cc
+++ b/libheif/nclx.cc
@@ -294,9 +294,11 @@ struct heif_color_profile_nclx* color_profile_nclx::alloc_nclx_color_profile()
 
   if (profile) {
     profile->version = 1;
-    profile->color_primaries = heif_color_primaries_ITU_R_BT_709_5;
-    profile->transfer_characteristics = heif_transfer_characteristic_IEC_61966_2_1;
-    profile->matrix_coefficients = heif_matrix_coefficients_ITU_R_BT_709_5;
+
+    // sRGB defaults
+    profile->color_primaries = heif_color_primaries_ITU_R_BT_709_5; // 1
+    profile->transfer_characteristics = heif_transfer_characteristic_IEC_61966_2_1; // 13
+    profile->matrix_coefficients = heif_matrix_coefficients_ITU_R_BT_470_6_System_B_G; // 5
     profile->full_range_flag = true;
   }
 
@@ -312,9 +314,10 @@ void color_profile_nclx::free_nclx_color_profile(struct heif_color_profile_nclx*
 
 void color_profile_nclx::set_default()
 {
+  // sRGB defaults
   m_colour_primaries = 1;
   m_transfer_characteristics = 13;
-  m_matrix_coefficients = 1;
+  m_matrix_coefficients = 5;
   m_full_range_flag = true;
 }
 
@@ -339,10 +342,10 @@ void color_profile_nclx::set_from_heif_color_profile_nclx(const struct heif_colo
 }
 
 
-void color_profile_nclx::replace_undefined_values_with_defaults()
+void color_profile_nclx::replace_undefined_values_with_sRGB_defaults()
 {
   if (m_matrix_coefficients == heif_matrix_coefficients_unspecified) {
-    m_matrix_coefficients = heif_matrix_coefficients_ITU_R_BT_709_5;
+    m_matrix_coefficients = heif_matrix_coefficients_ITU_R_BT_470_6_System_B_G;
   }
 
   if (m_colour_primaries == heif_color_primaries_unspecified) {
diff --git a/libheif/nclx.h b/libheif/nclx.h
index 12c0448057..ad832752dd 100644
--- a/libheif/nclx.h
+++ b/libheif/nclx.h
@@ -159,7 +159,7 @@ class color_profile_nclx : public color_profile
 
   void set_from_heif_color_profile_nclx(const struct heif_color_profile_nclx* nclx);
 
-  void replace_undefined_values_with_defaults();
+  void replace_undefined_values_with_sRGB_defaults();
 
 private:
   uint16_t m_colour_primaries = heif_color_primaries_unspecified;