diff --git a/src/v_2ddrawer.cpp b/src/v_2ddrawer.cpp
index b45b671f9..40cea9904 100644
--- a/src/v_2ddrawer.cpp
+++ b/src/v_2ddrawer.cpp
@@ -574,10 +574,10 @@ void F2DDrawer::AddColorOnlyQuad(int x1, int y1, int w, int h, PalEntry color, F
 //
 //==========================================================================
 
-void F2DDrawer::AddLine(int x1, int y1, int x2, int y2, int palcolor, uint32_t color)
+void F2DDrawer::AddLine(int x1, int y1, int x2, int y2, int palcolor, uint32_t color, uint8_t alpha)
 {
 	PalEntry p = color ? (PalEntry)color : GPalette.BaseColors[palcolor];
-	p.a = 255;
+	p.a = alpha;
 
 	RenderCommand dg;
 
@@ -596,9 +596,10 @@ void F2DDrawer::AddLine(int x1, int y1, int x2, int y2, int palcolor, uint32_t c
 //
 //==========================================================================
 
-void F2DDrawer::AddThickLine(int x1, int y1, int x2, int y2, double thickness, uint32_t color)
+void F2DDrawer::AddThickLine(int x1, int y1, int x2, int y2, double thickness, uint32_t color, uint8_t alpha)
 {
 	PalEntry p = (PalEntry)color;
+	p.a = alpha;
 
 	DVector2 point0(x1, y1);
 	DVector2 point1(x2, y2);
diff --git a/src/v_2ddrawer.h b/src/v_2ddrawer.h
index e9079de3d..9f7f16676 100644
--- a/src/v_2ddrawer.h
+++ b/src/v_2ddrawer.h
@@ -139,8 +139,8 @@ public:
 	void AddClear(int left, int top, int right, int bottom, int palcolor, uint32_t color);
 	
 		
-	void AddLine(int x1, int y1, int x2, int y2, int palcolor, uint32_t color);
-	void AddThickLine(int x1, int y1, int x2, int y2, double thickness, uint32_t color);
+	void AddLine(int x1, int y1, int x2, int y2, int palcolor, uint32_t color, uint8_t alpha = 255);
+	void AddThickLine(int x1, int y1, int x2, int y2, double thickness, uint32_t color, uint8_t alpha = 255);
 	void AddPixel(int x1, int y1, int palcolor, uint32_t color);
 
 	void Clear();
diff --git a/src/v_draw.cpp b/src/v_draw.cpp
index e3babb060..f2b5a7800 100644
--- a/src/v_draw.cpp
+++ b/src/v_draw.cpp
@@ -1075,9 +1075,9 @@ void DFrameBuffer::FillBorder (FTexture *img)
 //
 //==========================================================================
 
-void DFrameBuffer::DrawLine(int x0, int y0, int x1, int y1, int palColor, uint32_t realcolor)
+void DFrameBuffer::DrawLine(int x0, int y0, int x1, int y1, int palColor, uint32_t realcolor, uint8_t alpha)
 {
-	m2DDrawer.AddLine(x0, y0, x1, y1, palColor, realcolor);
+	m2DDrawer.AddLine(x0, y0, x1, y1, palColor, realcolor, alpha);
 }
 
 DEFINE_ACTION_FUNCTION(_Screen, DrawLine)
@@ -1088,13 +1088,14 @@ DEFINE_ACTION_FUNCTION(_Screen, DrawLine)
 	PARAM_INT(x1);
 	PARAM_INT(y1);
 	PARAM_INT(color);
+	PARAM_INT_DEF(alpha);
 	if (!screen->HasBegun2D()) ThrowAbortException(X_OTHER, "Attempt to draw to screen outside a draw function");
-	screen->DrawLine(x0, y0, x1, y1, -1, color);
+	screen->DrawLine(x0, y0, x1, y1, -1, color, alpha);
 	return 0;
 }
 
-void DFrameBuffer::DrawThickLine(int x0, int y0, int x1, int y1, double thickness, uint32_t realcolor) {
-	m2DDrawer.AddThickLine(x0, y0, x1, y1, thickness, realcolor);
+void DFrameBuffer::DrawThickLine(int x0, int y0, int x1, int y1, double thickness, uint32_t realcolor, uint8_t alpha) {
+	m2DDrawer.AddThickLine(x0, y0, x1, y1, thickness, realcolor, alpha);
 }
 
 DEFINE_ACTION_FUNCTION(_Screen, DrawThickLine)
@@ -1106,8 +1107,9 @@ DEFINE_ACTION_FUNCTION(_Screen, DrawThickLine)
 	PARAM_INT(y1);
 	PARAM_FLOAT(thickness);
 	PARAM_INT(color);
+	PARAM_INT_DEF(alpha);
 	if (!screen->HasBegun2D()) ThrowAbortException(X_OTHER, "Attempt to draw to screen outside a draw function");
-	screen->DrawThickLine(x0, y0, x1, y1, thickness, color);
+	screen->DrawThickLine(x0, y0, x1, y1, thickness, color, alpha);
 	return 0;
 }
 
diff --git a/src/v_video.h b/src/v_video.h
index 75db34bf2..b2fe73657 100644
--- a/src/v_video.h
+++ b/src/v_video.h
@@ -535,10 +535,10 @@ public:
 	void Clear(int left, int top, int right, int bottom, int palcolor, uint32_t color);
 
 	// Draws a line
-	void DrawLine(int x0, int y0, int x1, int y1, int palColor, uint32_t realcolor);
+	void DrawLine(int x0, int y0, int x1, int y1, int palColor, uint32_t realcolor, uint8_t alpha = 255);
 
 	// Draws a line with thickness
-	void DrawThickLine(int x0, int y0, int x1, int y1, double thickness, uint32_t realcolor);
+	void DrawThickLine(int x0, int y0, int x1, int y1, double thickness, uint32_t realcolor, uint8_t alpha = 255);
 
 	// Draws a single pixel
 	void DrawPixel(int x, int y, int palcolor, uint32_t rgbcolor);
diff --git a/wadsrc/static/zscript/base.txt b/wadsrc/static/zscript/base.txt
index e648febd1..9ae1452e5 100644
--- a/wadsrc/static/zscript/base.txt
+++ b/wadsrc/static/zscript/base.txt
@@ -193,8 +193,8 @@ struct Screen native
 	native static vararg void DrawShape(TextureID tex, bool animate, Shape2D s, ...);
 	native static vararg void DrawChar(Font font, int normalcolor, double x, double y, int character, ...);
 	native static vararg void DrawText(Font font, int normalcolor, double x, double y, String text, ...);
-	native static void DrawLine(int x0, int y0, int x1, int y1, Color color);
-	native static void DrawThickLine(int x0, int y0, int x1, int y1, double thickness, Color color);
+	native static void DrawLine(int x0, int y0, int x1, int y1, Color color, int alpha = 255);
+	native static void DrawThickLine(int x0, int y0, int x1, int y1, double thickness, Color color, int alpha = 255);
 	native static void DrawFrame(int x, int y, int w, int h);
 	native static Vector2, Vector2 VirtualToRealCoords(Vector2 pos, Vector2 size, Vector2 vsize, bool vbottom=false, bool handleaspect=true);
 	native static double GetAspectRatio();