diff --git a/kleidicv/src/filters/gaussian_blur_neon.cpp b/kleidicv/src/filters/gaussian_blur_neon.cpp
index 003d8de8ad2624808c10bdf90f4cffc75b9ac9ff..c560227961e6c48729aac5a0a3a53f309124d3ba 100644
--- a/kleidicv/src/filters/gaussian_blur_neon.cpp
+++ b/kleidicv/src/filters/gaussian_blur_neon.cpp
@@ -705,7 +705,7 @@ static kleidicv_error_t gaussian_blur_checks(
   CHECK_IMAGE_SIZE(width, height);
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   if (workspace->channels() < channels) {
diff --git a/kleidicv/src/filters/gaussian_blur_sc.h b/kleidicv/src/filters/gaussian_blur_sc.h
index 2e65f0317ea67d37f604741538171758f0723439..936ee012a09f7640ec043388f09252449d8d87bd 100644
--- a/kleidicv/src/filters/gaussian_blur_sc.h
+++ b/kleidicv/src/filters/gaussian_blur_sc.h
@@ -1074,7 +1074,7 @@ static kleidicv_error_t gaussian_blur_checks(
   CHECK_IMAGE_SIZE(width, height);
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   if (workspace->channels() < channels) {
diff --git a/kleidicv/src/filters/separable_filter_2d_api.cpp b/kleidicv/src/filters/separable_filter_2d_api.cpp
index 276b49628b7787f00a0ea76fd4dc19647389730b..79f0edeb7f8203cb4ebcf25d5c01f1041ed4f438 100644
--- a/kleidicv/src/filters/separable_filter_2d_api.cpp
+++ b/kleidicv/src/filters/separable_filter_2d_api.cpp
@@ -73,7 +73,7 @@ kleidicv_error_t kleidicv_filter_context_create(
   }
 
   if (max_channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   CHECK_IMAGE_SIZE(max_image_width, max_image_height);
diff --git a/kleidicv/src/filters/separable_filter_2d_neon.cpp b/kleidicv/src/filters/separable_filter_2d_neon.cpp
index 6aec3082a6523ea46ca20e54fd30d4a0316b4d9b..a8eb9fa6b8ea17c6788fcebbe2d6afea07a24e47 100644
--- a/kleidicv/src/filters/separable_filter_2d_neon.cpp
+++ b/kleidicv/src/filters/separable_filter_2d_neon.cpp
@@ -327,7 +327,7 @@ static kleidicv_error_t separable_filter_2d_checks(
   CHECK_IMAGE_SIZE(width, height);
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   if (workspace->channels() < channels) {
diff --git a/kleidicv/src/filters/separable_filter_2d_sc.h b/kleidicv/src/filters/separable_filter_2d_sc.h
index a98a3f8ecd2caf0daa7d7a8de77f1d7efa69cc1e..ad270c47576f525d575ec82eff06f41a3cb7a9f4 100644
--- a/kleidicv/src/filters/separable_filter_2d_sc.h
+++ b/kleidicv/src/filters/separable_filter_2d_sc.h
@@ -447,7 +447,7 @@ static kleidicv_error_t separable_filter_2d_checks(
   CHECK_IMAGE_SIZE(width, height);
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   if (workspace->channels() < channels) {
diff --git a/kleidicv/src/filters/sobel_neon.cpp b/kleidicv/src/filters/sobel_neon.cpp
index 137921fe9ef566c900daadbe756c76d3841a6a78..0e2b69e1bab9eeada501ea714f5b04954adea2c2 100644
--- a/kleidicv/src/filters/sobel_neon.cpp
+++ b/kleidicv/src/filters/sobel_neon.cpp
@@ -137,7 +137,7 @@ kleidicv_error_t sobel_3x3_horizontal_stripe_s16_u8(
   CHECK_IMAGE_SIZE(width, height);
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   Rectangle rect{width, height};
@@ -167,7 +167,7 @@ kleidicv_error_t sobel_3x3_vertical_stripe_s16_u8(
   CHECK_IMAGE_SIZE(width, height);
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   Rectangle rect{width, height};
diff --git a/kleidicv/src/filters/sobel_sc.h b/kleidicv/src/filters/sobel_sc.h
index be3167d4f5715f6a5ea62018b3f7536e4f5b9020..341c152d5166a9536852bc26e362c51e0c74d041 100644
--- a/kleidicv/src/filters/sobel_sc.h
+++ b/kleidicv/src/filters/sobel_sc.h
@@ -129,7 +129,7 @@ static kleidicv_error_t sobel_3x3_horizontal_stripe_s16_u8_sc(
   CHECK_IMAGE_SIZE(width, height);
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   Rectangle rect{width, height};
@@ -159,7 +159,7 @@ static kleidicv_error_t sobel_3x3_vertical_stripe_s16_u8_sc(
   CHECK_IMAGE_SIZE(width, height);
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   Rectangle rect{width, height};
diff --git a/kleidicv/src/morphology/morphology_api.cpp b/kleidicv/src/morphology/morphology_api.cpp
index 619224817c5082d1f2792d8b25da1789221cacf9..71607bbb314f87506e128c1be2824e48b7b3c98e 100644
--- a/kleidicv/src/morphology/morphology_api.cpp
+++ b/kleidicv/src/morphology/morphology_api.cpp
@@ -71,7 +71,7 @@ kleidicv_error_t kleidicv_morphology_create(
   }
 
   if (channels > KLEIDICV_MAXIMUM_CHANNEL_COUNT) {
-    return KLEIDICV_ERROR_RANGE;
+    return KLEIDICV_ERROR_NOT_IMPLEMENTED;
   }
 
   auto morphology_border_type =
diff --git a/test/api/test_gaussian_blur.cpp b/test/api/test_gaussian_blur.cpp
index 2a8c28c17d79e94e6de29a8b87fa9e2921062ead..6c54487fc76e997d31416b4cf53ae672395370d6 100644
--- a/test/api/test_gaussian_blur.cpp
+++ b/test/api/test_gaussian_blur.cpp
@@ -1119,7 +1119,7 @@ TYPED_TEST(GaussianBlur, ChannelNumber) {
   ASSERT_EQ(KLEIDICV_OK, kleidicv_filter_context_create(&context, 1, 15, 15,
                                                         validSize, validSize));
   TypeParam src[1], dst[1];
-  EXPECT_EQ(KLEIDICV_ERROR_RANGE,
+  EXPECT_EQ(KLEIDICV_ERROR_NOT_IMPLEMENTED,
             gaussian_blur<TypeParam>()(
                 src, sizeof(TypeParam), dst, sizeof(TypeParam), validSize,
                 validSize, KLEIDICV_MAXIMUM_CHANNEL_COUNT + 1, 15, 15, 0.0, 0.0,
diff --git a/test/api/test_morphology.cpp b/test/api/test_morphology.cpp
index eb8a9bbbd858d67f5c0764e37dba81a1ea9f2e47..a7258d05a565da4d11ee275c31927001f2d327b4 100644
--- a/test/api/test_morphology.cpp
+++ b/test/api/test_morphology.cpp
@@ -445,7 +445,7 @@ TYPED_TEST(Morphology, UnsupportedChannels) {
   kleidicv_border_type_t border = KLEIDICV_BORDER_TYPE_REPLICATE;
   const uint8_t border_value[] = {0, 0, 1, 1};
 
-  EXPECT_EQ(KLEIDICV_ERROR_RANGE,
+  EXPECT_EQ(KLEIDICV_ERROR_NOT_IMPLEMENTED,
             kleidicv_morphology_create(&context, small_rect, anchor, border,
                                        border_value, 5, 1, sizeof(TypeParam),
                                        small_rect));
@@ -522,7 +522,7 @@ TYPED_TEST(Morphology, InvalidChannelNumber) {
   kleidicv_morphology_context_t *context = nullptr;
   const uint8_t border_value[] = {};
 
-  EXPECT_EQ(KLEIDICV_ERROR_RANGE,
+  EXPECT_EQ(KLEIDICV_ERROR_NOT_IMPLEMENTED,
             kleidicv_morphology_create(
                 &context, kleidicv_rectangle_t{1, 1}, kleidicv_point_t{0, 0},
                 KLEIDICV_BORDER_TYPE_REPLICATE, border_value,
diff --git a/test/api/test_separable_filter_2d.cpp b/test/api/test_separable_filter_2d.cpp
index 0b5d802746194254c396c1782e364f78fd85a232..8ac608c828a6b107fcbd36ca722528ca5938a148 100644
--- a/test/api/test_separable_filter_2d.cpp
+++ b/test/api/test_separable_filter_2d.cpp
@@ -729,7 +729,7 @@ TYPED_TEST(SeparableFilter2D, ChannelNumber) {
   ASSERT_EQ(KLEIDICV_OK, kleidicv_filter_context_create(&context, 1, 5, 5,
                                                         validSize, validSize));
   TypeParam src[1], dst[1], kernel[5] = {};
-  EXPECT_EQ(KLEIDICV_ERROR_RANGE,
+  EXPECT_EQ(KLEIDICV_ERROR_NOT_IMPLEMENTED,
             separable_filter_2d<TypeParam>()(
                 src, sizeof(TypeParam), dst, sizeof(TypeParam), validSize,
                 validSize, KLEIDICV_MAXIMUM_CHANNEL_COUNT + 1, kernel, 5,
@@ -864,7 +864,7 @@ TEST(FilterCreate, DifferentKernelSize) {
 TEST(FilterCreate, ChannelNumber) {
   kleidicv_filter_context_t *context = nullptr;
 
-  EXPECT_EQ(KLEIDICV_ERROR_RANGE,
+  EXPECT_EQ(KLEIDICV_ERROR_NOT_IMPLEMENTED,
             kleidicv_filter_context_create(
                 &context, KLEIDICV_MAXIMUM_CHANNEL_COUNT + 1, 1, 1, 1, 1));
   ASSERT_EQ(nullptr, context);
diff --git a/test/api/test_sobel.cpp b/test/api/test_sobel.cpp
index 41bf00c4744f069b0df4c199d5f2df6b4605a361..44158a096ee9b5b758c377d299f947488020226d 100644
--- a/test/api/test_sobel.cpp
+++ b/test/api/test_sobel.cpp
@@ -279,11 +279,11 @@ TYPED_TEST(Sobel, ChannelNumber) {
   typename KernelTestParams::OutputType dst[1];
   size_t validSize = 2;
 
-  EXPECT_EQ(KLEIDICV_ERROR_RANGE,
+  EXPECT_EQ(KLEIDICV_ERROR_NOT_IMPLEMENTED,
             sobel_3x3_horizontal<TypeParam>()(
                 src, sizeof(src), dst, sizeof(dst), validSize, validSize,
                 KLEIDICV_MAXIMUM_CHANNEL_COUNT + 1));
-  EXPECT_EQ(KLEIDICV_ERROR_RANGE,
+  EXPECT_EQ(KLEIDICV_ERROR_NOT_IMPLEMENTED,
             sobel_3x3_vertical<TypeParam>()(
                 src, sizeof(src), dst, sizeof(dst), validSize, validSize,
                 KLEIDICV_MAXIMUM_CHANNEL_COUNT + 1));