diff --git a/Source/UnitTest/test_encode.cpp b/Source/UnitTest/test_encode.cpp
index 069f6441..cc9be93c 100644
--- a/Source/UnitTest/test_encode.cpp
+++ b/Source/UnitTest/test_encode.cpp
@@ -96,6 +96,41 @@ TEST(compress, overflow_in_16)
 	astcenc_context_free(context);
 }
 
+/** @brief Input test for an out-of-range alpha-scale radius. */
+TEST(compress, ascale_radius_clamped)
+{
+	astcenc_error status;
+	astcenc_config config;
+	astcenc_context* context;
+
+	static const astcenc_swizzle swizzle {
+		ASTCENC_SWZ_R, ASTCENC_SWZ_G, ASTCENC_SWZ_B, ASTCENC_SWZ_A
+	};
+
+	astcenc_config_init(ASTCENC_PRF_LDR, 4, 4, 1, ASTCENC_PRE_MEDIUM, 0, &config);
+
+	// Set to largest possible value to check input validation
+	config.a_scale_radius = 0xFFFFFFFFu;
+	status = astcenc_context_alloc(&config, 1, &context, nullptr);
+	EXPECT_EQ(status, ASTCENC_SUCCESS);
+
+	uint8_t data[16];
+	uint8_t input[4 * 4 * 4];
+
+	astcenc_image image;
+	image.dim_x = 4;
+	image.dim_y = 4;
+	image.dim_z = 1;
+	image.data_type = ASTCENC_TYPE_U8;
+	uint8_t* slices = input;
+	image.data = reinterpret_cast<void**>(&slices);
+
+	// Compression should succeed without bad_alloc or ASAN failure
+	status = astcenc_compress_image(context, &image, &swizzle, data, sizeof(data), 0);
+	EXPECT_EQ(status, ASTCENC_SUCCESS);
+
+	astcenc_context_free(context);
+}
 
 /** @brief Input data buffer overrun tests. */
 TEST(compress, data_buffer_exceeded)
diff --git a/Source/astcenc_entry.cpp b/Source/astcenc_entry.cpp
index 79c65a0c..3e7dddf1 100644
--- a/Source/astcenc_entry.cpp
+++ b/Source/astcenc_entry.cpp
@@ -464,6 +464,9 @@ static astcenc_error validate_config(
 
 	config.rgbm_m_scale = astc::max(config.rgbm_m_scale, 1.0f);
 
+	// Clamp alpha-scale kernel radius to put an upper bound on memory use
+	config.a_scale_radius = astc::min(config.a_scale_radius, ALPHASCALE_MAX_RADIUS);
+
 	config.tune_partition_count_limit = astc::clamp(config.tune_partition_count_limit, 1u, 4u);
 	config.tune_2partition_index_limit = astc::clamp(config.tune_2partition_index_limit, 1u, BLOCK_MAX_PARTITIONINGS);
 	config.tune_3partition_index_limit = astc::clamp(config.tune_3partition_index_limit, 1u, BLOCK_MAX_PARTITIONINGS);
diff --git a/Source/astcenc_internal.h b/Source/astcenc_internal.h
index 46942171..ea3c1a42 100644
--- a/Source/astcenc_internal.h
+++ b/Source/astcenc_internal.h
@@ -120,6 +120,9 @@ static constexpr unsigned int WEIGHTS_MAX_DECIMATION_MODES { 87 };
 /** @brief The high default error used to initialize error trackers. */
 static constexpr float ERROR_CALC_DEFAULT { 1e30f };
 
+/** @brief The maximum alpha-scale kernel radius. */
+static constexpr unsigned int ALPHASCALE_MAX_RADIUS { 64 };
+
 /**
  * @brief The minimum tuning setting threshold for the one partition fast path.
  */