diff --git a/build.rs b/build.rs
index 30b5f05..3379da3 100644
--- a/build.rs
+++ b/build.rs
@@ -7,16 +7,20 @@
 
     let target = env::var("TARGET").unwrap();
 
-    if !enable_use_proc_macro(&target) {
-        return;
-    }
-    println!("cargo:rustc-cfg=use_proc_macro");
-
     let minor = match rustc_minor_version() {
         Some(n) => n,
         None => return,
     };
 
+    if minor >= 26 {
+        println!("cargo:rustc-cfg=u128");
+    }
+
+    if !enable_use_proc_macro(&target) {
+        return;
+    }
+    println!("cargo:rustc-cfg=use_proc_macro");
+
     // Rust 1.29 stabilized the necessary APIs in the `proc_macro` crate
     if minor >= 29 || cfg!(feature = "nightly") {
         println!("cargo:rustc-cfg=wrap_proc_macro");
diff --git a/src/lib.rs b/src/lib.rs
index ba9e67b..a26b117 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -973,6 +973,12 @@
         isize_suffixed => isize,
     }
 
+    #[cfg(u128)]
+    suffixed_int_literals! {
+        u128_suffixed => u128,
+        i128_suffixed => i128,
+    }
+
     unsuffixed_int_literals! {
         u8_unsuffixed => u8,
         u16_unsuffixed => u16,
@@ -986,6 +992,12 @@
         isize_unsuffixed => isize,
     }
 
+    #[cfg(u128)]
+    unsuffixed_int_literals! {
+        u128_unsuffixed => u128,
+        i128_unsuffixed => i128,
+    }
+
     pub fn f64_unsuffixed(f: f64) -> Literal {
         assert!(f.is_finite());
         Literal::_new(imp::Literal::f64_unsuffixed(f))
diff --git a/src/stable.rs b/src/stable.rs
index 6c06fc4..0d8aac9 100644
--- a/src/stable.rs
+++ b/src/stable.rs
@@ -678,6 +678,12 @@
         f64_suffixed => f64,
     }
 
+    #[cfg(u128)]
+    suffixed_numbers! {
+        u128_suffixed => u128,
+        i128_suffixed => i128,
+    }
+
     unsuffixed_numbers! {
         u8_unsuffixed => u8,
         u16_unsuffixed => u16,
@@ -691,6 +697,12 @@
         isize_unsuffixed => isize,
     }
 
+    #[cfg(u128)]
+    unsuffixed_numbers! {
+        u128_unsuffixed => u128,
+        i128_unsuffixed => i128,
+    }
+
     pub fn f32_unsuffixed(f: f32) -> Literal {
         let mut s = f.to_string();
         if !s.contains(".") {
diff --git a/src/unstable.rs b/src/unstable.rs
index 433639d..d15b9da 100644
--- a/src/unstable.rs
+++ b/src/unstable.rs
@@ -819,6 +819,12 @@
         f64_suffixed => f64,
     }
 
+    #[cfg(u128)]
+    suffixed_numbers! {
+        i128_suffixed => i128,
+        u128_suffixed => u128,
+    }
+
     unsuffixed_integers! {
         u8_unsuffixed => u8,
         u16_unsuffixed => u16,
@@ -832,6 +838,12 @@
         isize_unsuffixed => isize,
     }
 
+    #[cfg(u128)]
+    unsuffixed_integers! {
+        i128_unsuffixed => i128,
+        u128_unsuffixed => u128,
+    }
+
     pub fn f32_unsuffixed(f: f32) -> Literal {
         if nightly_works() {
             Literal::Nightly(proc_macro::Literal::f32_unsuffixed(f))