diff --git a/src/parsing.rs b/src/parsing.rs
index 3827d52..c3c2850 100644
--- a/src/parsing.rs
+++ b/src/parsing.rs
@@ -22,21 +22,23 @@ pub fn parse_number_with_radix<T: Num>(
     base: u32,
     limit: Option<usize>,
 ) -> Option<T> {
-    tokens.skip_tokens_while(|t| *t == ' ');
-    let mut remaining = limit.map(|x| x as isize).unwrap_or(isize::MAX);
-    let mut prefix = String::new();
-    if tokens.token('-') {
-        prefix.push('-');
-    }
-    let digits: String = tokens
-        .tokens_while(|c| {
-            remaining -= 1;
-            c.is_digit(base) && remaining >= 0
-        })
-        .collect();
-    (!digits.is_empty())
-        .then(|| T::from_str_radix(&format!("{}{}", prefix, digits), base).ok())
-        .flatten()
+    tokens.optional(|t| {
+        t.skip_tokens_while(|t| *t == ' ');
+        let mut remaining = limit.map(|x| x as isize).unwrap_or(isize::MAX);
+        let mut prefix = String::new();
+        if t.token('-') {
+            prefix.push('-');
+        }
+        let digits: String = t
+            .tokens_while(|c| {
+                remaining -= 1;
+                c.is_digit(base) && remaining >= 0
+            })
+            .collect();
+        (!digits.is_empty())
+            .then(|| T::from_str_radix(&format!("{}{}", prefix, digits), base).ok())
+            .flatten()
+    })
 }
 
 pub fn parse_n<R, T, I, P, S, const N: usize>(