diff --git a/matrix.go b/matrix.go
index 85ba0b8..3776ee7 100644
--- a/matrix.go
+++ b/matrix.go
@@ -110,7 +110,7 @@ func (c *HardwareConfig) geometry() (width, height int) {
 
 func (c *RunTimeConfig) rt_options() *C.struct_RGBLedRuntimeOptions {
 	rt := &C.struct_RGBLedRuntimeOptions{}
-	rt.gpio_slowdown = C.int(c.gpio_slowdown)
+	rt.gpio_slowdown = C.int(c.Gpio_slowdown)
 
 	return rt
 }