diff --git a/content/canvas/src/nsCanvasRenderingContext2D.cpp b/content/canvas/src/nsCanvasRenderingContext2D.cpp
index edbfa93f7d0..a651ee0b610 100644
--- a/content/canvas/src/nsCanvasRenderingContext2D.cpp
+++ b/content/canvas/src/nsCanvasRenderingContext2D.cpp
@@ -3168,8 +3168,8 @@ nsCanvasRenderingContext2D::GetLineJoin(nsAString& joinstyle)
 NS_IMETHODIMP
 nsCanvasRenderingContext2D::SetMiterLimit(float miter)
 {
-    if (!FloatValidate(miter))
-        return NS_ERROR_DOM_SYNTAX_ERR;
+    if (!FloatValidate(miter) || miter <= 0.0)
+        return NS_OK;
 
     mThebes->SetMiterLimit(miter);
     return NS_OK;
diff --git a/content/canvas/test/test_canvas.html b/content/canvas/test/test_canvas.html
index babcd7dc95a..0e055a1a03c 100644
--- a/content/canvas/test/test_canvas.html
+++ b/content/canvas/test/test_canvas.html
@@ -9829,28 +9829,28 @@ ok(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
 
 ctx.miterLimit = 1.5;
 ctx.miterLimit = 0;
-todo(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
+ok(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
 
 ctx.miterLimit = 1.5;
 ctx.miterLimit = -1;
-todo(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
+ok(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
 
 ctx.miterLimit = 1.5;
 ctx.miterLimit = Infinity;
-todo(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
+ok(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
 
 ctx.miterLimit = 1.5;
 ctx.miterLimit = -Infinity;
-todo(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
+ok(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
 
 ctx.miterLimit = 1.5;
 ctx.miterLimit = NaN;
-todo(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
+ok(ctx.miterLimit === 1.5, "ctx.miterLimit === 1.5");
 
 } catch (e) {
     _thrown_outer = true;
 }
-todo(!_thrown_outer, 'should not throw exception');
+ok(!_thrown_outer, 'should not throw exception');
 
 
 }