diff --git a/libavfilter/vf_colorchannelmixer.c b/libavfilter/vf_colorchannelmixer.c
index e6c6fe3c5d..3bbe44d6ef 100644
--- a/libavfilter/vf_colorchannelmixer.c
+++ b/libavfilter/vf_colorchannelmixer.c
@@ -125,7 +125,7 @@ static av_always_inline int filter_slice_rgba_planar(AVFilterContext *ctx, void
             const uint8_t rin = srcr[j];
             const uint8_t gin = srcg[j];
             const uint8_t bin = srcb[j];
-            const uint8_t ain = srca[j];
+            const uint8_t ain = have_alpha ? srca[j] : 0;
 
             dstr[j] = av_clip_uint8(s->lut[R][R][rin] +
                                     s->lut[R][G][gin] +
@@ -184,7 +184,7 @@ static av_always_inline int filter_slice_rgba16_planar(AVFilterContext *ctx, voi
             const uint16_t rin = srcr[j];
             const uint16_t gin = srcg[j];
             const uint16_t bin = srcb[j];
-            const uint16_t ain = srca[j];
+            const uint16_t ain = have_alpha ? srca[j] : 0;
 
             dstr[j] = av_clip_uintp2(s->lut[R][R][rin] +
                                      s->lut[R][G][gin] +