diff --git a/source/blender/blenkernel/BKE_image.h b/source/blender/blenkernel/BKE_image.h
index e36d4bab566..f7fd7450734 100644
--- a/source/blender/blenkernel/BKE_image.h
+++ b/source/blender/blenkernel/BKE_image.h
@@ -73,7 +73,7 @@ int     BKE_imtype_supports_zbuf(const char imtype);
 int     BKE_imtype_supports_compress(const char imtype);
 int     BKE_imtype_supports_quality(const char imtype);
 int     BKE_imtype_requires_linear_float(const char imtype);
-char    BKE_imtype_valid_channels(const char imtype);
+char    BKE_imtype_valid_channels(const char imtype, bool write_file);
 char    BKE_imtype_valid_depths(const char imtype);
 
 char    BKE_imtype_from_arg(const char *arg);
diff --git a/source/blender/blenkernel/intern/image.c b/source/blender/blenkernel/intern/image.c
index 7d8ada0fa68..b74424a1d28 100644
--- a/source/blender/blenkernel/intern/image.c
+++ b/source/blender/blenkernel/intern/image.c
@@ -1161,16 +1161,18 @@ int BKE_imtype_requires_linear_float(const char imtype)
 	return 0;
 }
 
-char BKE_imtype_valid_channels(const char imtype)
+char BKE_imtype_valid_channels(const char imtype, bool write_file)
 {
 	char chan_flag = IMA_CHAN_FLAG_RGB; /* assume all support rgb */
 
 	/* alpha */
 	switch (imtype) {
+		case R_IMF_IMTYPE_BMP:
+			if (write_file) break;
+			/* fall-through */
 		case R_IMF_IMTYPE_TARGA:
 		case R_IMF_IMTYPE_IRIS:
 		case R_IMF_IMTYPE_PNG:
-		/* case R_IMF_IMTYPE_BMP: */ /* read but not write */
 		case R_IMF_IMTYPE_RADHDR:
 		case R_IMF_IMTYPE_TIFF:
 		case R_IMF_IMTYPE_OPENEXR:
diff --git a/source/blender/editors/space_image/image_buttons.c b/source/blender/editors/space_image/image_buttons.c
index 21f54a86df4..f88cdaf6713 100644
--- a/source/blender/editors/space_image/image_buttons.c
+++ b/source/blender/editors/space_image/image_buttons.c
@@ -753,7 +753,7 @@ void uiTemplateImage(uiLayout *layout, bContext *C, PointerRNA *ptr, const char
 
 					if (ibuf) {
 						int imtype = BKE_ftype_to_imtype(ibuf->ftype);
-						char valid_channels = BKE_imtype_valid_channels(imtype);
+						char valid_channels = BKE_imtype_valid_channels(imtype, false);
 
 						has_alpha = (valid_channels & IMA_CHAN_FLAG_ALPHA) != 0;
 
diff --git a/source/blender/makesrna/intern/rna_scene.c b/source/blender/makesrna/intern/rna_scene.c
index 90d14a7ba6f..0c70e332053 100644
--- a/source/blender/makesrna/intern/rna_scene.c
+++ b/source/blender/makesrna/intern/rna_scene.c
@@ -729,7 +729,7 @@ static void rna_ImageFormatSettings_file_format_set(PointerRNA *ptr, int value)
 	ID *id = ptr->id.data;
 	const char is_render = (id && GS(id->name) == ID_SCE);
 	/* see note below on why this is */
-	const char chan_flag = BKE_imtype_valid_channels(imf->imtype) | (is_render ? IMA_CHAN_FLAG_BW : 0);
+	const char chan_flag = BKE_imtype_valid_channels(imf->imtype, true) | (is_render ? IMA_CHAN_FLAG_BW : 0);
 
 	imf->imtype = value;
 
@@ -800,7 +800,7 @@ static EnumPropertyItem *rna_ImageFormatSettings_color_mode_itemf(bContext *UNUS
 	 * where 'BW' will force grayscale even if the output format writes
 	 * as RGBA, this is age old blender convention and not sure how useful
 	 * it really is but keep it for now - campbell */
-	char chan_flag = BKE_imtype_valid_channels(imf->imtype) | (is_render ? IMA_CHAN_FLAG_BW : 0);
+	char chan_flag = BKE_imtype_valid_channels(imf->imtype, true) | (is_render ? IMA_CHAN_FLAG_BW : 0);
 
 #ifdef WITH_FFMPEG
 	/* a WAY more crappy case than B&W flag: depending on codec, file format MIGHT support