diff --git a/tests/color-icc-output-test.c b/tests/color-icc-output-test.c
index 2f2de05e..682e10c7 100644
--- a/tests/color-icc-output-test.c
+++ b/tests/color-icc-output-test.c
@@ -175,7 +175,7 @@ test_roundtrip(uint8_t r, uint8_t g, uint8_t b, cmsPipeline *pip,
 	struct color_float out = {};
 
 	cmsPipelineEvalFloat(in.rgb, out.rgb, pip);
-	rgb_diff_stat_update(stat, &in, &out);
+	rgb_diff_stat_update(stat, &in, &out, &in);
 }
 
 /*
diff --git a/tests/color_util.c b/tests/color_util.c
index da2f5c6b..9267aefe 100644
--- a/tests/color_util.c
+++ b/tests/color_util.c
@@ -449,7 +449,8 @@ rgb_diff_stat_print(const struct rgb_diff_stat *stat,
 void
 rgb_diff_stat_update(struct rgb_diff_stat *stat,
 		     const struct color_float *ref,
-		     const struct color_float *val)
+		     const struct color_float *val,
+		     const struct color_float *pos)
 {
 	unsigned i;
 	double ssd = 0.0;
@@ -457,9 +458,9 @@ rgb_diff_stat_update(struct rgb_diff_stat *stat,
 	for (i = 0; i < COLOR_CHAN_NUM; i++) {
 		double diff = val->rgb[i] - ref->rgb[i];
 
-		scalar_stat_update(&stat->rgb[i], diff, ref);
+		scalar_stat_update(&stat->rgb[i], diff, pos);
 		ssd += diff * diff;
 	}
 
-	scalar_stat_update(&stat->two_norm, sqrt(ssd), ref);
+	scalar_stat_update(&stat->two_norm, sqrt(ssd), pos);
 }
diff --git a/tests/color_util.h b/tests/color_util.h
index 1bb7297a..9ad09588 100644
--- a/tests/color_util.h
+++ b/tests/color_util.h
@@ -164,7 +164,8 @@ scalar_stat_print_float(const struct scalar_stat *stat);
 void
 rgb_diff_stat_update(struct rgb_diff_stat *stat,
 		     const struct color_float *ref,
-		     const struct color_float *val);
+		     const struct color_float *val,
+		     const struct color_float *pos);
 
 void
 rgb_diff_stat_print(const struct rgb_diff_stat *stat,