diff --git a/HISTORY.md b/HISTORY.md
index ee37f99cc..a00e40ade 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -1,5 +1,10 @@
 # History
 
+# unpublished changes since 13.0.2
+
+- Fix: #3232 fix type definitions of function `format` to support notations
+  `hex`, `bin`, and `oct`.
+
 # 2024-07-04, 13.0.2
 
 - Fix an error in the type definitions of `quantileSeq` (#3223).
diff --git a/test/typescript-tests/testTypes.ts b/test/typescript-tests/testTypes.ts
index d3419a2c6..738963ae4 100644
--- a/test/typescript-tests/testTypes.ts
+++ b/test/typescript-tests/testTypes.ts
@@ -2168,6 +2168,9 @@ Factory Test
   const d = divide(a, b)
   assert.strictEqual(format(c), '16/21')
   assert.strictEqual(format(d), '7/9')
+  assert.strictEqual(format(255, { notation: 'bin' }), '0b11111111')
+  assert.strictEqual(format(255, { notation: 'hex' }), '0xff')
+  assert.strictEqual(format(255, { notation: 'oct' }), '0o377')
 }
 
 /**
diff --git a/types/index.d.ts b/types/index.d.ts
index 37603ac13..fd4e1f0c3 100644
--- a/types/index.d.ts
+++ b/types/index.d.ts
@@ -4352,7 +4352,14 @@ export interface FormatOptions {
    * elsewhere. Lower bound is included, upper bound is excluded. For
    * example '123.4' and '1.4e7'.
    */
-  notation?: 'fixed' | 'exponential' | 'engineering' | 'auto'
+  notation?:
+    | 'fixed'
+    | 'exponential'
+    | 'engineering'
+    | 'auto'
+    | 'hex'
+    | 'bin'
+    | 'oct'
 
   /**
    * A number between 0 and 16 to round the digits of the number. In case