diff --git a/src/dsp/lossless.c b/src/dsp/lossless.c
index d05af84e..b2fbf174 100644
--- a/src/dsp/lossless.c
+++ b/src/dsp/lossless.c
@@ -167,15 +167,20 @@ static uint32_t Predictor13_C(uint32_t left, const uint32_t* const top) {
   return pred;
 }
 
-GENERATE_PREDICTOR_ADD(Predictor0_C, PredictorAdd0_C)
+static void PredictorAdd0_C(const uint32_t* in, const uint32_t* upper,
+                            int num_pixels, uint32_t* out) {
+  int x;
+  (void)upper;
+  for (x = 0; x < num_pixels; ++x) out[x] = VP8LAddPixels(in[x], ARGB_BLACK);
+}
 static void PredictorAdd1_C(const uint32_t* in, const uint32_t* upper,
                             int num_pixels, uint32_t* out) {
   int i;
   uint32_t left = out[-1];
+  (void)upper;
   for (i = 0; i < num_pixels; ++i) {
     out[i] = left = VP8LAddPixels(in[i], left);
   }
-  (void)upper;
 }
 GENERATE_PREDICTOR_ADD(Predictor2_C, PredictorAdd2_C)
 GENERATE_PREDICTOR_ADD(Predictor3_C, PredictorAdd3_C)
diff --git a/src/dsp/lossless_common.h b/src/dsp/lossless_common.h
index a2648d17..9c2ebe68 100644
--- a/src/dsp/lossless_common.h
+++ b/src/dsp/lossless_common.h
@@ -177,6 +177,7 @@ uint32_t VP8LSubPixels(uint32_t a, uint32_t b) {
 static void PREDICTOR_ADD(const uint32_t* in, const uint32_t* upper, \
                           int num_pixels, uint32_t* out) {           \
   int x;                                                             \
+  assert(upper != NULL);                                             \
   for (x = 0; x < num_pixels; ++x) {                                 \
     const uint32_t pred = (PREDICTOR)(out[x - 1], upper + x);        \
     out[x] = VP8LAddPixels(in[x], pred);                             \
@@ -189,6 +190,7 @@ static void PREDICTOR_ADD(const uint32_t* in, const uint32_t* upper, \
 static void PREDICTOR_SUB(const uint32_t* in, const uint32_t* upper, \
                           int num_pixels, uint32_t* out) {           \
   int x;                                                             \
+  assert(upper != NULL);                                             \
   for (x = 0; x < num_pixels; ++x) {                                 \
     const uint32_t pred = (PREDICTOR)(in[x - 1], upper + x);         \
     out[x] = VP8LSubPixels(in[x], pred);                             \