diff --git a/docs/src/content/docs/api-output.md b/docs/src/content/docs/api-output.md
index b6729c63..25ad70c6 100644
--- a/docs/src/content/docs/api-output.md
+++ b/docs/src/content/docs/api-output.md
@@ -717,7 +717,7 @@ instead of providing `xres` and `yres` in pixels/mm.
 | [options.xres] | <code>number</code> | <code>1.0</code> | horizontal resolution in pixels/mm |
 | [options.yres] | <code>number</code> | <code>1.0</code> | vertical resolution in pixels/mm |
 | [options.resolutionUnit] | <code>string</code> | <code>&quot;&#x27;inch&#x27;&quot;</code> | resolution unit options: inch, cm |
-| [options.bitdepth] | <code>number</code> | <code>8</code> | reduce bitdepth to 1, 2 or 4 bit |
+| [options.bitdepth] | <code>number</code> | <code>0</code> | reduce bitdepth to 1, 2 or 4 bit |
 | [options.miniswhite] | <code>boolean</code> | <code>false</code> | write 1-bit images as miniswhite |
 
 **Example**  
diff --git a/docs/src/content/docs/changelog/v0.35.0.md b/docs/src/content/docs/changelog/v0.35.0.md
index 9f97d0e3..f047aab4 100644
--- a/docs/src/content/docs/changelog/v0.35.0.md
+++ b/docs/src/content/docs/changelog/v0.35.0.md
@@ -20,6 +20,8 @@ slug: changelog/v0.35.0
 
 * Upgrade to libvips v8.18.0 for upstream bug fixes.
 
+* Ensure TIFF output `bitdepth` option is limited to 1, 2 or 4.
+
 * Deprecate Windows 32-bit (win32-ia32) prebuilt binaries.
 
 * Add AVIF/HEIF `tune` option for control over quality metrics.
diff --git a/lib/constructor.js b/lib/constructor.js
index 1a2e55be..149d0b34 100644
--- a/lib/constructor.js
+++ b/lib/constructor.js
@@ -366,7 +366,7 @@ const Sharp = function (input, options) {
     tiffPredictor: 'horizontal',
     tiffPyramid: false,
     tiffMiniswhite: false,
-    tiffBitdepth: 8,
+    tiffBitdepth: 0,
     tiffTile: false,
     tiffTileHeight: 256,
     tiffTileWidth: 256,
diff --git a/lib/index.d.ts b/lib/index.d.ts
index fd36ecf9..b924ecf8 100644
--- a/lib/index.d.ts
+++ b/lib/index.d.ts
@@ -1479,8 +1479,8 @@ declare namespace sharp {
         xres?: number | undefined;
         /** Vertical resolution in pixels/mm (optional, default 1.0) */
         yres?: number | undefined;
-        /** Reduce bitdepth to 1, 2 or 4 bit (optional, default 8) */
-        bitdepth?: 1 | 2 | 4 | 8 | undefined;
+        /** Reduce bitdepth to 1, 2 or 4 bit (optional) */
+        bitdepth?: 1 | 2 | 4 | undefined;
         /** Write 1-bit images as miniswhite (optional, default false) */
         miniswhite?: boolean | undefined;
         /** Resolution unit options: inch, cm (optional, default 'inch') */
diff --git a/lib/output.js b/lib/output.js
index d0e1d3d5..b0213f5e 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -1055,7 +1055,7 @@ function trySetAnimationOptions (source, target) {
  * @param {number} [options.xres=1.0] - horizontal resolution in pixels/mm
  * @param {number} [options.yres=1.0] - vertical resolution in pixels/mm
  * @param {string} [options.resolutionUnit='inch'] - resolution unit options: inch, cm
- * @param {number} [options.bitdepth=8] - reduce bitdepth to 1, 2 or 4 bit
+ * @param {number} [options.bitdepth=0] - reduce bitdepth to 1, 2 or 4 bit
  * @param {boolean} [options.miniswhite=false] - write 1-bit images as miniswhite
  * @returns {Sharp}
  * @throws {Error} Invalid options
@@ -1070,10 +1070,10 @@ function tiff (options) {
       }
     }
     if (is.defined(options.bitdepth)) {
-      if (is.integer(options.bitdepth) && is.inArray(options.bitdepth, [1, 2, 4, 8])) {
+      if (is.integer(options.bitdepth) && is.inArray(options.bitdepth, [1, 2, 4])) {
         this.options.tiffBitdepth = options.bitdepth;
       } else {
-        throw is.invalidParameterError('bitdepth', '1, 2, 4 or 8', options.bitdepth);
+        throw is.invalidParameterError('bitdepth', '1, 2 or 4', options.bitdepth);
       }
     }
     // tiling
diff --git a/src/pipeline.h b/src/pipeline.h
index a007f7a8..dfd50393 100644
--- a/src/pipeline.h
+++ b/src/pipeline.h
@@ -365,7 +365,7 @@ struct PipelineBaton {
     tiffBigtiff(false),
     tiffPredictor(VIPS_FOREIGN_TIFF_PREDICTOR_HORIZONTAL),
     tiffPyramid(false),
-    tiffBitdepth(8),
+    tiffBitdepth(0),
     tiffMiniswhite(false),
     tiffTile(false),
     tiffTileHeight(256),
diff --git a/test/unit/tiff.js b/test/unit/tiff.js
index be5e5535..21c46ace 100644
--- a/test/unit/tiff.js
+++ b/test/unit/tiff.js
@@ -122,7 +122,6 @@ describe('TIFF', () => {
     sharp(fixtures.inputTiff8BitDepth)
       .toColourspace('b-w') // can only squash 1 band uchar images
       .tiff({
-        bitdepth: 8,
         compression: 'none',
         predictor: 'none'
       })
@@ -154,7 +153,7 @@ describe('TIFF', () => {
   it('Invalid TIFF bitdepth value throws error', () => {
     assert.throws(() => {
       sharp().tiff({ bitdepth: 3 });
-    }, /Error: Expected 1, 2, 4 or 8 for bitdepth but received 3 of type number/);
+    }, /Error: Expected 1, 2 or 4 for bitdepth but received 3 of type number/);
   });
 
   it('TIFF setting xres and yres on file', () =>