diff --git a/types/core/Program.d.ts b/types/core/Program.d.ts
index 2c63999d..936bc783 100644
--- a/types/core/Program.d.ts
+++ b/types/core/Program.d.ts
@@ -51,7 +51,7 @@ export class Program {
 
     setShaders(options: { vertex: string; fragment: string }): void;
 
-    setBlendFunc(src: GLenum, dst: GLenum, srcAlpha: GLenum, dstAlpha: GLenum): void;
+    setBlendFunc(src: GLenum, dst: GLenum, srcAlpha?: GLenum, dstAlpha?: GLenum): void;
 
     setBlendEquation(modeRGB: GLenum, modeAlpha: GLenum): void;
 
diff --git a/types/core/Renderer.d.ts b/types/core/Renderer.d.ts
index 6612f7c7..b4485e35 100644
--- a/types/core/Renderer.d.ts
+++ b/types/core/Renderer.d.ts
@@ -118,7 +118,7 @@ export class Renderer {
 
     disable(id: GLenum): void;
 
-    setBlendFunc(src: GLenum, dst: GLenum, srcAlpha: GLenum, dstAlpha: GLenum): void;
+    setBlendFunc(src: GLenum, dst: GLenum, srcAlpha?: GLenum, dstAlpha?: GLenum): void;
 
     setBlendEquation(modeRGB: GLenum, modeAlpha: GLenum): void;