diff --git a/Outputs/CRT/CRTOpenGL.cpp b/Outputs/CRT/CRTOpenGL.cpp
index 89513778d..70afeff00 100644
--- a/Outputs/CRT/CRTOpenGL.cpp
+++ b/Outputs/CRT/CRTOpenGL.cpp
@@ -375,7 +375,7 @@ void CRT::prepare_shader()
 	glUniform2f(positionConversionUniform, _horizontal_flywheel->get_scan_period(), _vertical_flywheel->get_scan_period() / (unsigned int)_vertical_flywheel_output_divider);
 
 	float scan_angle = atan2f(1.0f / (float)_height_of_display, 1.0f);
-	float scan_normal[] = { sinf(scan_angle), cosf(scan_angle)};
+	float scan_normal[] = { -sinf(scan_angle), cosf(scan_angle)};
 	float multiplier = (float)_horizontal_flywheel->get_standard_period() / ((float)_height_of_display * (float)_horizontal_flywheel->get_scan_period());
 	scan_normal[0] *= multiplier;
 	scan_normal[1] *= multiplier;