diff --git a/platform/darwin/test/MGLExpressionTests.mm b/platform/darwin/test/MGLExpressionTests.mm
index e853c68fb7b..53c86e37afd 100644
--- a/platform/darwin/test/MGLExpressionTests.mm
+++ b/platform/darwin/test/MGLExpressionTests.mm
@@ -520,6 +520,18 @@ - (void)testTypeConversionExpressionObject {
         // because it returns a primitive instead of an object.
         XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
     }
+    {
+        NSExpression *expression = [NSExpression expressionWithFormat:@"FUNCTION(postalCode, 'mgl_number')"];
+        NSArray *jsonExpression = @[@"to-number", @[@"get", @"postalCode"]];
+        XCTAssertEqualObjects(expression.mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression expressionWithFormat:@"FUNCTION(postalCode, 'doubleValue')"].mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression expressionWithFormat:@"FUNCTION(postalCode, 'floatValue')"].mgl_jsonExpressionObject, jsonExpression);
+        XCTAssertEqualObjects([NSExpression expressionWithFormat:@"FUNCTION(postalCode, 'decimalValue')"].mgl_jsonExpressionObject, jsonExpression);
+        // NSExpression is unable to evaluate NSNumber’s -floatValue,
+        // -doubleValue, or -decimalValue by themselves because they each return
+        // a primitive instead of an object.
+        XCTAssertEqualObjects([NSExpression mgl_expressionWithJSONObject:jsonExpression], expression);
+    }
     {
         NSExpression *expression = [NSExpression expressionWithFormat:@"FUNCTION(postalCode, 'mgl_numberWithFallbackValues:', zipCode)"];
         NSArray *jsonExpression = @[@"to-number", @[@"get", @"postalCode"], @[@"get", @"zipCode"]];