diff --git a/src/input/shared.rs b/src/input/shared.rs
index e99bfabcf..f4251a11d 100644
--- a/src/input/shared.rs
+++ b/src/input/shared.rs
@@ -1,3 +1,5 @@
+use std::borrow::Cow;
+
 use pyo3::prelude::*;
 use pyo3::sync::GILOnceCell;
 use pyo3::{intern, Py, PyAny, Python};
@@ -61,17 +63,19 @@ fn strip_underscores(s: &str) -> Option<String> {
     // Double consecutive underscores are also not valid
     // If there are no underscores at all, no need to replace anything
     if s.starts_with('_') || s.ends_with('_') || !s.contains('_') || s.contains("__") {
-        // no underscores to strip
-        return None;
+        // no underscores to strip, or underscores in the wrong place
+        None
+    } else {
+        Some(s.replace('_', ""))
     }
-    Some(s.replace('_', ""))
 }
 
 /// parse a string as an int
+/// max length of the input is 4300 which is checked by jiter, see
+/// https://docs.python.org/3/whatsnew/3.11.html#other-cpython-implementation-changes and
+/// https://github.com/python/cpython/issues/95778 for more info in that length bound
 pub fn str_as_int<'py>(input: &(impl Input<'py> + ?Sized), str: &str) -> ValResult<EitherInt<'py>> {
-    let str = str.trim();
-
-    // we have to call `NumberInt::try_from` directly first so we fail fast if the string is too long
+    // we can't move `NumberInt::try_from` into its own function we fail fast if the string is too long
     match NumberInt::try_from(str.as_bytes()) {
         Ok(NumberInt::Int(i)) => return Ok(EitherInt::I64(i)),
         Ok(NumberInt::BigInt(i)) => return Ok(EitherInt::BigInt(i)),
@@ -82,10 +86,12 @@ pub fn str_as_int<'py>(input: &(impl Input<'py> + ?Sized), str: &str) -> ValResu
         }
     }
 
-    if let Some(str_stripped) = strip_decimal_zeros(str) {
-        _parse_str(input, str_stripped)
-    } else if let Some(str_stripped) = strip_underscores(str) {
-        _parse_str(input, &str_stripped)
+    if let Some(cleaned_str) = clean_int_str(str) {
+        match NumberInt::try_from(cleaned_str.as_ref().as_bytes()) {
+            Ok(NumberInt::Int(i)) => Ok(EitherInt::I64(i)),
+            Ok(NumberInt::BigInt(i)) => Ok(EitherInt::BigInt(i)),
+            Err(_) => Err(ValError::new(ErrorTypeDefaults::IntParsing, input)),
+        }
     } else {
         Err(ValError::new(ErrorTypeDefaults::IntParsing, input))
     }
@@ -102,30 +108,32 @@ pub fn str_as_float<'py>(input: &(impl Input<'py> + ?Sized), str: &str) -> ValRe
     }
 }
 
-/// parse a string as an int, `input` is required here to get lifetimes to match up
-/// max length of the input is 4300 which is checked by jiter, see
-/// https://docs.python.org/3/whatsnew/3.11.html#other-cpython-implementation-changes and
-/// https://github.com/python/cpython/issues/95778 for more info in that length bound
-fn _parse_str<'py>(input: &(impl Input<'py> + ?Sized), str: &str) -> ValResult<EitherInt<'py>> {
-    match NumberInt::try_from(str.as_bytes()) {
-        Ok(jiter::NumberInt::Int(i)) => Ok(EitherInt::I64(i)),
-        Ok(jiter::NumberInt::BigInt(i)) => Ok(EitherInt::BigInt(i)),
-        Err(e) => match e.error_type {
-            JsonErrorType::NumberOutOfRange => Err(ValError::new(ErrorTypeDefaults::IntParsingSize, input)),
-            _ => Err(ValError::new(ErrorTypeDefaults::IntParsing, input)),
-        },
-    }
-}
+fn clean_int_str(mut s: &str) -> Option<Cow<str>> {
+    let len_before = s.len();
+
+    // strip leading and trailing whitespace
+    s = s.trim();
 
-/// we don't want to parse as f64 then call `float_as_int` as it can loose precision for large ints, therefore
-/// we strip `.0+` manually instead, then parse as i64
-fn strip_decimal_zeros(s: &str) -> Option<&str> {
+    // strip loading zeros
+    s = s.trim_start_matches('0');
+
+    // we don't want to parse as f64 then call `float_as_int` as it can lose precision for large ints, therefore
+    // we strip `.0+` manually instead
     if let Some(i) = s.find('.') {
         if s[i + 1..].chars().all(|c| c == '0') {
-            return Some(&s[..i]);
+            s = &s[..i];
+        }
+    }
+
+    // remove underscores
+    if let Some(str_stripped) = strip_underscores(s) {
+        Some(str_stripped.into())
+    } else {
+        match len_before == s.len() {
+            true => None,
+            false => Some(s.into()),
         }
     }
-    None
 }
 
 pub fn float_as_int<'py>(input: &(impl Input<'py> + ?Sized), float: f64) -> ValResult<EitherInt<'py>> {
diff --git a/tests/validators/test_int.py b/tests/validators/test_int.py
index baddb6289..775c65cc3 100644
--- a/tests/validators/test_int.py
+++ b/tests/validators/test_int.py
@@ -26,6 +26,11 @@
         ('42', 42),
         (42.0, 42),
         ('42.0', 42),
+        ('042', 42),
+        ('4_2', 42),
+        ('4_2.0', 42),
+        ('04_2.0', 42),
+        ('000001', 1),
         ('123456789.0', 123_456_789),
         ('123456789123456.00001', Err('Input should be a valid integer, unable to parse string as an integer')),
         (int(1e10), int(1e10)),