diff --git a/video/img_format.c b/video/img_format.c
index 3dbd94fe62..8d2b0d058b 100644
--- a/video/img_format.c
+++ b/video/img_format.c
@@ -553,7 +553,7 @@ static bool get_native_desc(int mpfmt, struct mp_imgfmt_desc *desc)
     return true;
 }
 
-int mp_imgfmt_desc_get_num_comps(struct mp_imgfmt_desc *desc)
+int mp_imgfmt_desc_get_num_comps(const struct mp_imgfmt_desc *desc)
 {
     int flags = desc->flags;
     if (!(flags & MP_IMGFLAG_COLOR_MASK))
diff --git a/video/img_format.h b/video/img_format.h
index 5f2044c944..8cc7788d76 100644
--- a/video/img_format.h
+++ b/video/img_format.h
@@ -147,7 +147,7 @@ struct mp_imgfmt_desc {
 struct mp_imgfmt_desc mp_imgfmt_get_desc(int imgfmt);
 
 // Return the number of component types, or 0 if unknown.
-int mp_imgfmt_desc_get_num_comps(struct mp_imgfmt_desc *desc);
+int mp_imgfmt_desc_get_num_comps(const struct mp_imgfmt_desc *desc);
 
 // For MP_IMGFLAG_PACKED_SS_YUV formats (packed sub-sampled YUV): positions of
 // further luma samples. luma_offsets must be an array of align_x size, and the