diff --git a/src/basic/Line.js b/src/basic/Line.js
index b2295d4c..3d143109 100644
--- a/src/basic/Line.js
+++ b/src/basic/Line.js
@@ -113,7 +113,10 @@ var Line = Base.extend(/** @lends Line# */{
     },
 
     isCollinear: function(line) {
-        return this._vx * line._vy - this._vy * line._vx < 1e-10;
+        // TODO: Tests showed that 1e-10 might work well here, but we want to
+        // keep it in sync with Point#isCollinear()
+        return this._vx * line._vy - this._vy * line._vx
+                < /*#=*/Numerical.TOLERANCE;
     },
 
     statics: /** @lends Line */{
diff --git a/src/basic/Point.js b/src/basic/Point.js
index 7ff1ab5a..f9af8718 100644
--- a/src/basic/Point.js
+++ b/src/basic/Point.js
@@ -703,7 +703,8 @@ var Point = Base.extend(/** @lends Point# */{
      */
     isCollinear: function(point) {
         // NOTE: Numerical.EPSILON is too small, breaking shape-path-shape
-        // conversion test.
+        // conversion test. But tolerance is probably too large?
+        // TODO: Tests showed that 1e-10 might work well here.
         return Math.abs(this.cross(point)) < /*#=*/Numerical.TOLERANCE;
     },