diff --git a/headers/enduro2d/utils/image.hpp b/headers/enduro2d/utils/image.hpp
index 95d0d4eb..032c0dd7 100644
--- a/headers/enduro2d/utils/image.hpp
+++ b/headers/enduro2d/utils/image.hpp
@@ -20,9 +20,7 @@ namespace e2d
         jpg,
         png,
         pvr,
-        tga,
-
-        unknown
+        tga
     };
 
     enum class image_data_format : u8 {
@@ -39,9 +37,7 @@ namespace e2d
         rgb_pvrtc4,
 
         rgba_pvrtc2,
-        rgba_pvrtc4,
-
-        unknown
+        rgba_pvrtc4
     };
 
     class bad_image_access final : public exception {
@@ -94,7 +90,7 @@ namespace e2d
     private:
         buffer data_;
         v2u size_;
-        image_data_format format_ = image_data_format::unknown;
+        image_data_format format_ = image_data_format::rgba8;
     };
 
     void swap(image& l, image& r) noexcept;
diff --git a/sources/enduro2d/utils/image.cpp b/sources/enduro2d/utils/image.cpp
index 966588c7..68018302 100644
--- a/sources/enduro2d/utils/image.cpp
+++ b/sources/enduro2d/utils/image.cpp
@@ -32,9 +32,7 @@ namespace
         {8,  2, image_data_format::rgb_pvrtc2,  true,  true,  true},
         {8,  4, image_data_format::rgb_pvrtc4,  true,  true,  true},
         {8,  2, image_data_format::rgba_pvrtc2, true,  true,  true},
-        {8,  4, image_data_format::rgba_pvrtc4, true,  true,  true},
-
-        {0,  0, image_data_format::unknown,     false, false, false}
+        {8,  4, image_data_format::rgba_pvrtc4, true,  true,  true}
     };
 
     const data_format_description& get_data_format_description(image_data_format format) noexcept {
@@ -67,8 +65,7 @@ namespace
     }
 
     bool check_image_format(const v2u& size, image_data_format format) noexcept {
-        return size == adjust_image_size(size, format)
-            && (format != image_data_format::unknown || size == v2u::zero());
+        return size == adjust_image_size(size, format);
     }
 
     bool check_image_format(const v2u& size, image_data_format format, const buffer& data) noexcept {
@@ -164,7 +161,7 @@ namespace e2d
     void image::clear() noexcept {
         data_.clear();
         size_ = v2u::zero();
-        format_ = image_data_format::unknown;
+        format_ = image_data_format::rgba8;
     }
 
     bool image::empty() const noexcept {
@@ -183,9 +180,7 @@ namespace e2d
         const data_format_description& format_desc =
             get_data_format_description(format_);
 
-        if ( empty() || u >= size_.x || v >= size_.y ) {
-            throw bad_image_access();
-        } else if ( format_desc.format == image_data_format::unknown || format_desc.compressed ) {
+        if ( empty() || u >= size_.x || v >= size_.y || format_desc.compressed ) {
             throw bad_image_access();
         }
 
@@ -303,8 +298,6 @@ namespace e2d { namespace images
                 return impl::try_save_image_pvr(src, dst);
             case image_file_format::tga:
                 return impl::try_save_image_tga(src, dst);
-            case image_file_format::unknown:
-                return false;
             default:
                 E2D_ASSERT_MSG(false, "unexpected image file format");
                 return false;
diff --git a/sources/enduro2d/utils/image_impl/image_reader_stb.cpp b/sources/enduro2d/utils/image_impl/image_reader_stb.cpp
index 94447fdf..907287bb 100644
--- a/sources/enduro2d/utils/image_impl/image_reader_stb.cpp
+++ b/sources/enduro2d/utils/image_impl/image_reader_stb.cpp
@@ -48,11 +48,13 @@ namespace
 
     image_data_format image_format_from_stb_channels(u32 channels) noexcept {
         switch ( channels ) {
-            case 1:  return image_data_format::g8;
-            case 2:  return image_data_format::ga8;
-            case 3:  return image_data_format::rgb8;
-            case 4:  return image_data_format::rgba8;
-            default: return image_data_format::unknown;
+            case 1: return image_data_format::g8;
+            case 2: return image_data_format::ga8;
+            case 3: return image_data_format::rgb8;
+            case 4: return image_data_format::rgba8;
+            default:
+                E2D_ASSERT_MSG(false, "unexpected stb channel count");
+                return image_data_format::rgba8;
         }
     }
 
@@ -61,7 +63,7 @@ namespace
     {
         try {
             const image_data_format img_format = image_format_from_stb_channels(img_channels);
-            if ( img && img_size.x > 0 && img_size.y > 0 && img_format != image_data_format::unknown ) {
+            if ( img && img_size.x > 0 && img_size.y > 0 ) {
                 buffer img_buffer(
                     img.get(),
                     math::numeric_cast<std::size_t>(img_size.x * img_size.y * img_channels));
diff --git a/untests/sources/untests_utils/image.cpp b/untests/sources/untests_utils/image.cpp
index 268f4719..c14ab301 100644
--- a/untests/sources/untests_utils/image.cpp
+++ b/untests/sources/untests_utils/image.cpp
@@ -11,29 +11,7 @@ TEST_CASE("images") {
     {
         image i;
         REQUIRE(i.size() == v2u::zero());
-        REQUIRE(i.format() == image_data_format::unknown);
-        REQUIRE(i.data().empty());
-        REQUIRE(i.empty());
-    }
-    {
-        image i(v2u::zero(), image_data_format::unknown);
-        REQUIRE(i.size() == v2u::zero());
-        REQUIRE(i.format() == image_data_format::unknown);
-        REQUIRE(i.data().empty());
-        REQUIRE(i.empty());
-    }
-    {
-        image i(v2u::zero(), image_data_format::unknown, buffer());
-        REQUIRE(i.size() == v2u::zero());
-        REQUIRE(i.format() == image_data_format::unknown);
-        REQUIRE(i.data().empty());
-        REQUIRE(i.empty());
-    }
-    {
-        const buffer b{};
-        image i(v2u::zero(), image_data_format::unknown, b);
-        REQUIRE(i.size() == v2u::zero());
-        REQUIRE(i.format() == image_data_format::unknown);
+        REQUIRE(i.format() == image_data_format::rgba8);
         REQUIRE(i.data().empty());
         REQUIRE(i.empty());
     }