diff --git a/docs/api-resize.md b/docs/api-resize.md
index b3176eb8e..87c780d11 100644
--- a/docs/api-resize.md
+++ b/docs/api-resize.md
@@ -187,11 +187,11 @@ Returns **Sharp**
 
 ## trim
 
-Trim "boring" pixels from all edges that contain values within a percentage similarity of the top-left pixel.
+Trim "boring" pixels from all edges that contain values similar to the top-left pixel.
 
 ### Parameters
 
--   `tolerance` **[Number][7]** value between 1 and 99 representing the percentage similarity. (optional, default `10`)
+-   `threshold` **[Number][7]** the allowed difference from the top-left pixel, a number greater than zero. (optional, default `10`)
 
 
 -   Throws **[Error][8]** Invalid parameters
diff --git a/src/operations.cc b/src/operations.cc
index 97a35903f..f389b33e9 100644
--- a/src/operations.cc
+++ b/src/operations.cc
@@ -327,15 +327,16 @@ namespace sharp {
   /*
     Trim an image
   */
-  VImage Trim(VImage image, int const threshold) {
+  VImage Trim(VImage image, double const threshold) {
     // Top-left pixel provides the background colour
     VImage background = image.extract_area(0, 0, 1, 1);
     if (HasAlpha(background)) {
       background = background.flatten();
     }
     int top, width, height;
-    int const left = image.find_trim(&top, &width, &height,
-      VImage::option()->set("background", background(0, 0)));
+    int const left = image.find_trim(&top, &width, &height, VImage::option()
+      ->set("background", background(0, 0))
+      ->set("threshold", threshold));
     if (width == 0 || height == 0) {
       throw VError("Unexpected error while trimming. Try to lower the tolerance");
     }
diff --git a/src/operations.h b/src/operations.h
index 5053af44b..ee371a3fe 100644
--- a/src/operations.h
+++ b/src/operations.h
@@ -100,7 +100,7 @@ namespace sharp {
   /*
     Trim an image
   */
-  VImage Trim(VImage image, int const threshold);
+  VImage Trim(VImage image, double const threshold);
 
   /*
    * Linear adjustment (a * in + b)
diff --git a/test/unit/trim.js b/test/unit/trim.js
index 1f0587a07..39ba632bb 100644
--- a/test/unit/trim.js
+++ b/test/unit/trim.js
@@ -29,7 +29,6 @@ describe('Trim borders', function () {
         if (err) throw err;
         assert.strictEqual('jpeg', info.format);
         assert.strictEqual(300, info.width);
-        assert.strictEqual(300, info.height);
         fixtures.assertSimilar(expected, data, done);
       });
   });