diff --git a/cmd/rv/probe_circleci.go b/cmd/rv/probe_circleci.go
index 3c82038e..060424d1 100644
--- a/cmd/rv/probe_circleci.go
+++ b/cmd/rv/probe_circleci.go
@@ -40,7 +40,7 @@ type turbidityProbe struct {
 }
 
 // NewTurbidityProbe returns an empty turbidity probe for CircleCI testing only.
-func NewTurbidityProbe(log logger.Logger, delay time.Duration) (*turbidityProbe, error) {
+func NewTurbidityProbe(log logger.Logger, delay time.Duration, transformMatrix []float64) (*turbidityProbe, error) {
 	tp := new(turbidityProbe)
 	return tp, nil
 }
diff --git a/revid/config/config_test.go b/revid/config/config_test.go
index 4983d2bd..d2a25a2f 100644
--- a/revid/config/config_test.go
+++ b/revid/config/config_test.go
@@ -122,6 +122,7 @@ func TestUpdate(t *testing.T) {
 		"VBRQuality":        "excellent",
 		"VerticalFlip":      "true",
 		"Width":             "300",
+		"TransformMatrix":   "0.1,  0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8,0.9",
 	}
 
 	dl := &dumbLogger{}
@@ -172,6 +173,7 @@ func TestUpdate(t *testing.T) {
 		VBRQuality:        QualityExcellent,
 		VerticalFlip:      true,
 		Width:             300,
+		TransformMatrix:   []float64{0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9},
 	}
 
 	got := Config{Logger: dl}
diff --git a/revid/config/variables.go b/revid/config/variables.go
index 8098eb68..fc52dd5a 100644
--- a/revid/config/variables.go
+++ b/revid/config/variables.go
@@ -149,13 +149,19 @@ var Variables = []struct {
 		Name: KeyTransformMatrix,
 		Type: typeString,
 		Update: func(c *Config, v string) {
-			v = strings.Replace(v, " ", "", 0)
+			c.Logger.Log(logger.Debug, "updating transform matrix", "string", v)
+			v = strings.Replace(v, " ", "", -1)
+			vals := make([]float64, 0)
+			if v == "" {
+				c.TransformMatrix = vals
+				return
+			}
+
 			elements := strings.Split(v, ",")
-			vals := make([]float64, len(elements))
-			for _, i := range elements {
-				vFloat, err := strconv.ParseFloat(i, 64)
+			for _, e := range elements {
+				vFloat, err := strconv.ParseFloat(e, 64)
 				if err != nil {
-					c.Logger.Log(logger.Warning, "invalid TransformMatrix param", "value", i)
+					c.Logger.Log(logger.Warning, "invalid TransformMatrix param", "value", e)
 				}
 				vals = append(vals, vFloat)
 			}