diff --git a/encoder/basisu_gpu_texture.cpp b/encoder/basisu_gpu_texture.cpp
index 23ef016..7627bb2 100644
--- a/encoder/basisu_gpu_texture.cpp
+++ b/encoder/basisu_gpu_texture.cpp
@@ -1527,13 +1527,13 @@ namespace basisu
 		case texture_format::cBC6HSigned:
 		{
 			internal_fmt = KTX_COMPRESSED_RGB_BPTC_SIGNED_FLOAT;
-			base_internal_fmt = KTX_RGBA;
+			base_internal_fmt = KTX_RGB;
 			break;
 		}
 		case texture_format::cBC6HUnsigned:
 		{
 			internal_fmt = KTX_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT;
-			base_internal_fmt = KTX_RGBA;
+			base_internal_fmt = KTX_RGB;
 			break;
 		}
 		case texture_format::cBC7:
@@ -1556,8 +1556,8 @@ namespace basisu
 		case texture_format::cASTC_HDR_6x6:
 		{
 			internal_fmt = KTX_COMPRESSED_RGBA_ASTC_6x6_KHR;
-			// TODO: should we write RGB? We don't support generating HDR 6x6 with alpha.
-			base_internal_fmt = KTX_RGBA; 
+			// RGBA is correct: ASTC HDR can have alpha, and the RGBA ASTC token's base format is RGBA.
+			base_internal_fmt = KTX_RGBA;
 			break;
 		}
 		// We use different enums for HDR vs. LDR ASTC, but internally they are both just ASTC.
diff --git a/transcoder/basisu_transcoder.h b/transcoder/basisu_transcoder.h
index 68b5ada..a317613 100644
--- a/transcoder/basisu_transcoder.h
+++ b/transcoder/basisu_transcoder.h
@@ -273,7 +273,7 @@ namespace basist
 		// Disable deblock filtering for XUASTC LDR/ASTC LDR transcoding to non-ASTC formats.
 		// For block sizes smaller than 10x8 (block area < BASISU_DEBLOCKING_BLOCK_SIZE_THRESHOLD texels), deblocking is disabled by default during encoding, but it can be enabled via compressor parameters.
 		// Note: The encoder writes a "DeblockFilterID" key value field into KTX2 files. By default (i.e. when neither this flag nor cDecodeFlagsForceDeblockFiltering
-		// is specified), the transcoder uses that field to decide if CPU deblocking should occur during transcoding. Specifying this flag, or
+		// is specified), the KTX2 transcoder uses that field to decide if CPU deblocking should occur during transcoding. Specifying this flag, or
 		// cDecodeFlagsForceDeblockFiltering, causes the transcoder to IGNORE the file's DeblockFilterID field and use the requested behavior instead.
 		cDecodeFlagsNoDeblockFiltering = 128,