diff --git a/compiler/src/passes/emit/elf/header.rs b/compiler/src/passes/emit/elf/header.rs
index 7f4e186..1c4b36c 100644
--- a/compiler/src/passes/emit/elf/header.rs
+++ b/compiler/src/passes/emit/elf/header.rs
@@ -1,6 +1,6 @@
-use std::clone::Clone;
 use crate::passes::emit::elf::program::ProgramHeader;
 use crate::passes::emit::elf::section::SectionHeader;
+use std::clone::Clone;
 use std::mem::size_of;
 use zerocopy::AsBytes;
 
diff --git a/compiler/src/passes/parse/mod.rs b/compiler/src/passes/parse/mod.rs
index e88b90c..54b75fc 100644
--- a/compiler/src/passes/parse/mod.rs
+++ b/compiler/src/passes/parse/mod.rs
@@ -336,9 +336,7 @@ pub enum BinaryOp {
 pub enum Lit<'p> {
     /// Integer literal, representing a signed 64-bit number.
     #[display(fmt = "{val}")]
-    Int {
-        val: &'p str,
-    },
+    Int { val: &'p str },
     /// Boolean literal, representing a value of *true* or *false*.
     #[display(fmt = "{}", r#"if *val { "true" } else { "false" }"#)]
     Bool { val: bool },
diff --git a/compiler/src/passes/validate/error.rs b/compiler/src/passes/validate/error.rs
index f9b997f..eadb104 100644
--- a/compiler/src/passes/validate/error.rs
+++ b/compiler/src/passes/validate/error.rs
@@ -85,11 +85,26 @@ pub enum TypeError {
         #[label = "The type definition `{sym}` is not sized."]
         span: (usize, usize),
     },
-    #[error("Integer out of bounds.")]
-    IntegerOutOfBounds {
-        #[label = "This number does not fit in type `{typ}`"]
+    #[error("Could not parse integer.")]
+    InvalidInteger {
+        #[label = "`{val}` is not a valid {typ}: {err}"]
         span: (usize, usize),
+        val: String,
         typ: &'static str,
+        err: String,
+    },
+    #[error("Could not parse integer.")]
+    InvalidByteLit {
+        #[label = "`{val}` is not a valid {typ}"]
+        span: (usize, usize),
+        val: String,
+        typ: &'static str,
+    },
+    #[error("Could not parse integer.")]
+    InvalidEscape {
+        #[label = "`{val}` is not an escape sequence (or has not been added to the compiler as an escape sequence!)"]
+        span: (usize, usize),
+        val: String,
     },
     #[error("Integer ambiguous.")]
     IntegerAmbiguous {
diff --git a/compiler/src/passes/validate/resolve.rs b/compiler/src/passes/validate/resolve.rs
index b9489df..48d3148 100644
--- a/compiler/src/passes/validate/resolve.rs
+++ b/compiler/src/passes/validate/resolve.rs
@@ -1,6 +1,7 @@
-use std::str::FromStr;
+use std::error::Error;
+use std::fmt::format;
 use crate::passes::parse::types::Type;
-use crate::passes::parse::{Constrained, Expr, Lit, Meta, Param, Spanned, TypeDef, Typed};
+use crate::passes::parse::{Constrained, Expr, Lit, Meta, Param, Spanned, TypeDef, Typed, Span};
 use crate::passes::select::{Instr, VarArg};
 use crate::passes::validate::error::TypeError;
 use crate::passes::validate::partial_type::PartialType;
@@ -12,6 +13,7 @@ use crate::utils::gen_sym::UniqueSym;
 use crate::utils::union_find::{UnionFind, UnionIndex};
 use crate::*;
 use functor_derive::Functor;
+use std::str::FromStr;
 
 impl<'p> PrgConstrained<'p> {
     pub fn resolve(mut self) -> Result<PrgValidated<'p>, TypeError> {
@@ -106,9 +108,52 @@ fn partial_type_to_type<'p>(
     })
 }
 
-fn resolve_int_lit<T: FromStr>(s: &str) -> T {
+fn resolve_int_lit(original_val: &str, span: Span) -> Result<i64, TypeError> {
+    let mut val = original_val;
+    if val.ends_with("i64") || val.ends_with("u64") {
+        val = &val[..val.len() - 3];
+    }
+
+    let (base, val) = match val {
+        s if s.starts_with("b") => {
+            let mut s = s[1..].chars();
 
-    todo!()
+            let int = match (s.next(), s.next(), s.next(), s.next(), s.next()) {
+                (Some('\''), Some(s), Some('\''), None, None) => {
+                    s as i64
+                },
+                (Some('\''), Some('\\'), Some(s), Some('\''), None) => {
+                    let int = match s {
+                        'n' => '\n',
+                        'r' => '\r',
+                        '\\' => '\\',
+                        '"' => '"',
+                        '\'' => '\'',
+                        '0' => '\0',
+                        s => return Err(TypeError::InvalidEscape {
+                            span,
+                            val: format!("\\{s}"),
+                        }),
+                    };
+                    int as i64
+                } ,
+                _ => unreachable!("Congrats you made an invalid byte lit, plx tell us how"),
+            };
+
+            return Ok(int)
+        }
+        s if s.starts_with("0b") => (2, &s[2..]),
+        s if s.starts_with("0o") => (8, &s[2..]),
+        s if s.starts_with("0x") => (16, &s[2..]),
+        s => (10, s),
+    };
+
+    i64::from_str_radix(&val.replace("_", ""), base).map_err(|error| TypeError::InvalidInteger {
+        span,
+        val: original_val.to_string(),
+        typ: "I64",
+        err: error.to_string(),
+    })
 }
 
 fn resolve_expr<'p>(
@@ -129,16 +174,10 @@ fn resolve_expr<'p>(
                     }
                     Some(typ) => match typ {
                         Type::I64 => TLit::I64 {
-                            val: val.trim_end_matches("i64").parse().map_err(|_| TypeError::IntegerOutOfBounds {
-                                span: expr.meta.span,
-                                typ: "I64",
-                            })?,
+                            val: resolve_int_lit(val, expr.meta.span)?,
                         },
                         Type::U64 => TLit::U64 {
-                            val: val.trim_end_matches("u64").parse().map_err(|_| TypeError::IntegerOutOfBounds {
-                                span: expr.meta.span,
-                                typ: "U64",
-                            })?,
+                            val: todo!(),
                         },
                         _ => unreachable!(),
                     },
diff --git a/programs/fail/validate/invalid_escape.test b/programs/fail/validate/invalid_escape.test
new file mode 100644
index 0000000..c0ea59b
--- /dev/null
+++ b/programs/fail/validate/invalid_escape.test
@@ -0,0 +1,4 @@
+//* err: InvalidEscape
+fn main() {
+    let x: I64 = b'\a';
+}
diff --git a/programs/fail/validate/integer_out_of_bounds.test b/programs/fail/validate/invalid_integer_1.test
similarity index 77%
rename from programs/fail/validate/integer_out_of_bounds.test
rename to programs/fail/validate/invalid_integer_1.test
index 053ba31..95b9b3f 100644
--- a/programs/fail/validate/integer_out_of_bounds.test
+++ b/programs/fail/validate/invalid_integer_1.test
@@ -1,4 +1,4 @@
-//* err: IntegerOutOfBounds
+//* err: InvalidInteger
 fn main() {
     // 9_223_372_036_854_775_807 is the max for an I64.
     9223372036854775808i64;
diff --git a/programs/fail/validate/invalid_integer_2.test b/programs/fail/validate/invalid_integer_2.test
new file mode 100644
index 0000000..fef7760
--- /dev/null
+++ b/programs/fail/validate/invalid_integer_2.test
@@ -0,0 +1,4 @@
+//* err: InvalidInteger
+fn main() {
+    1a2i64;
+}
diff --git a/programs/fail/validate/invalid_integer_3.test b/programs/fail/validate/invalid_integer_3.test
new file mode 100644
index 0000000..e382efa
--- /dev/null
+++ b/programs/fail/validate/invalid_integer_3.test
@@ -0,0 +1,4 @@
+//* err: InvalidInteger
+fn main() {
+    0b3i64;
+}
diff --git a/programs/good/mutability/semicolons.test b/programs/good/mutability/semicolons.test
index 2b0237a..1df3406 100644
--- a/programs/good/mutability/semicolons.test
+++ b/programs/good/mutability/semicolons.test
@@ -1,5 +1,5 @@
 fn main() -> Unit {
     5i64;
-    6u64;
+    6i64;
     7i64;
 }
diff --git a/programs/good/simple/wacky_literals.test b/programs/good/simple/wacky_literals.test
index 67f68b6..371f691 100644
--- a/programs/good/simple/wacky_literals.test
+++ b/programs/good/simple/wacky_literals.test
@@ -10,4 +10,6 @@ fn main() {
     let i: I64 = 0o52;
     let j: I64 = 0o5_2;
     let k: I64 = b'\n';         // sadly this is not 42
+    let l = b'*'i64;
+    let m = 4_2i64;
 }