diff --git a/content/canvas/src/nsCanvasRenderingContext2D.cpp b/content/canvas/src/nsCanvasRenderingContext2D.cpp
index a651ee0b610..b57bc39752e 100644
--- a/content/canvas/src/nsCanvasRenderingContext2D.cpp
+++ b/content/canvas/src/nsCanvasRenderingContext2D.cpp
@@ -3078,8 +3078,8 @@ nsCanvasRenderingContext2D::MozTextAlongPath(const nsAString& textToDraw, PRBool
 NS_IMETHODIMP
 nsCanvasRenderingContext2D::SetLineWidth(float width)
 {
-    if (!FloatValidate(width))
-        return NS_ERROR_DOM_SYNTAX_ERR;
+    if (!FloatValidate(width) || width <= 0.0)
+        return NS_OK;
 
     mThebes->SetLineWidth(width);
     return NS_OK;
diff --git a/content/canvas/test/test_canvas.html b/content/canvas/test/test_canvas.html
index 0e055a1a03c..e0069fc1c70 100644
--- a/content/canvas/test/test_canvas.html
+++ b/content/canvas/test/test_canvas.html
@@ -10119,28 +10119,28 @@ ok(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
 
 ctx.lineWidth = 1.5;
 ctx.lineWidth = 0;
-todo(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
+ok(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
 
 ctx.lineWidth = 1.5;
 ctx.lineWidth = -1;
-todo(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
+ok(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
 
 ctx.lineWidth = 1.5;
 ctx.lineWidth = Infinity;
-todo(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
+ok(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
 
 ctx.lineWidth = 1.5;
 ctx.lineWidth = -Infinity;
-todo(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
+ok(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
 
 ctx.lineWidth = 1.5;
 ctx.lineWidth = NaN;
-todo(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
+ok(ctx.lineWidth === 1.5, "ctx.lineWidth === 1.5");
 
 } catch (e) {
     _thrown_outer = true;
 }
-todo(!_thrown_outer, 'should not throw exception');
+ok(!_thrown_outer, 'should not throw exception');
 
 
 }