diff --git a/lib/yargs-parser.ts b/lib/yargs-parser.ts
index 48a2d0f2..5116b8ec 100644
--- a/lib/yargs-parser.ts
+++ b/lib/yargs-parser.ts
@@ -637,7 +637,13 @@ export class YargsParser {
       return value
     }
 
-    function maybeCoerceNumber (key: string, value: string | number | null | undefined) {
+    function maybeCoerceNumber (key: string, value: unknown) {
+      // Coercion callbacks may intentionally return objects (for example,
+      // parsed connection strings). Only strings and numbers can be inspected
+      // for numeric syntax; passing other values to the regular expressions
+      // in `looksLikeNumber` can throw for objects without a prototype.
+      if (typeof value !== 'string' && typeof value !== 'number') return value
+
       if (!configuration['parse-positional-numbers'] && key === '_') return value
       if (!checkAllAliases(key, flags.strings) && !checkAllAliases(key, flags.bools) && !Array.isArray(value)) {
         const shouldCoerceNumber = looksLikeNumber(value) && configuration['parse-numbers'] && (
diff --git a/test/yargs-parser.mjs b/test/yargs-parser.mjs
index 4c692375..d5c4cae9 100644
--- a/test/yargs-parser.mjs
+++ b/test/yargs-parser.mjs
@@ -3536,6 +3536,21 @@ describe('yargs-parser', function () {
       parsed.foo.should.equal('BAR')
     })
 
+    it('preserves objects returned by coercion functions', function () {
+      const value = Object.create(null)
+      value.database = 'postgres'
+
+      const parsed = parser(['--connection', 'postgresql://db/example'], {
+        coerce: {
+          connection: function () {
+            return value
+          }
+        }
+      })
+
+      parsed.connection.should.equal(value)
+    })
+
     it('applies coercion function to an implicit array', function () {
       const parsed = parser(['--foo', '99', '-f', '33'], {
         coerce: {