diff --git a/sway-lib-std/src/lib.sw b/sway-lib-std/src/lib.sw
index 76aad2cd846..249ffc21ce5 100644
--- a/sway-lib-std/src/lib.sw
+++ b/sway-lib-std/src/lib.sw
@@ -13,10 +13,10 @@ pub mod registers;
 pub mod iterator;
 pub mod vec;
 pub mod bytes;
-pub mod primitive_conversions;
 pub mod math;
 pub mod flags;
 pub mod u128;
+pub mod primitive_conversions;
 pub mod alias;
 pub mod hash;
 pub mod asset_id;
diff --git a/sway-lib-std/src/primitive_conversions/b256.sw b/sway-lib-std/src/primitive_conversions/b256.sw
index 52d3157c500..9e267da1adc 100644
--- a/sway-lib-std/src/primitive_conversions/b256.sw
+++ b/sway-lib-std/src/primitive_conversions/b256.sw
@@ -3,6 +3,7 @@ library;
 use ::bytes::Bytes;
 use ::convert::{From, TryFrom};
 use ::option::Option::{self, *};
+use ::u128::U128;
 
 impl TryFrom<Bytes> for b256 {
     fn try_from(b: Bytes) -> Option<Self> {
@@ -37,6 +38,35 @@ impl From<u256> for b256 {
     }
 }
 
+impl From<U128> for b256 {
+    /// Converts a `U128` to a `b256`.
+    ///
+    /// # Arguments
+    ///
+    /// * `num`: [U128] - The `U128` to be converted.
+    ///
+    /// # Returns
+    ///
+    /// * [b256] - The `b256` representation of the `U128` value.
+    ///
+    /// # Examples
+    ///
+    /// ```sway
+    /// use std::u128::U128;
+    ///
+    /// fn foo() {
+    ///    let u128_value = U128::from((18446744073709551615_u64, 18446744073709551615_u64));
+    ///    let b256_value = b256::from(u128_value);
+    /// }
+    /// ```
+    fn from(num: U128) -> Self {
+        let input = (0u64, 0u64, num.upper(), num.lower());
+        asm(input: input) {
+            input: b256
+        }
+    }
+}
+
 impl From<(u64, u64, u64, u64)> for b256 {
     /// Casts a tuple of 4 `u64` values to a `b256`.
     ///
@@ -103,6 +133,16 @@ fn test_b256_from_u256() {
     assert(res == 0x0000000000000000000000000000000000000000000000000000000000000000);
 }
 
+#[test]
+fn test_b256_from_u128() {
+    use ::assert::assert;
+
+    let b256_value = <b256 as From<U128>>::from(U128::from((18446744073709551615_u64, 18446744073709551615_u64)));
+    assert(
+        b256_value == 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff,
+    );
+}
+
 #[test]
 fn test_b256_from_tuple() {
     use ::assert::assert;
diff --git a/sway-lib-std/src/primitive_conversions/u256.sw b/sway-lib-std/src/primitive_conversions/u256.sw
index 8e840404cd5..3acfcf97539 100644
--- a/sway-lib-std/src/primitive_conversions/u256.sw
+++ b/sway-lib-std/src/primitive_conversions/u256.sw
@@ -1,6 +1,7 @@
 library;
 
 use ::convert::From;
+use ::u128::U128;
 
 /// Functions for casting between `u256` and other types.
 impl From<u8> for u256 {
@@ -124,6 +125,35 @@ impl From<b256> for u256 {
     }
 }
 
+impl From<U128> for u256 {
+    /// Converts a `U128` to a `u256`.
+    ///
+    /// # Arguments
+    ///
+    /// * `num`: [U128] - The `U128` to be converted.
+    ///
+    /// # Returns
+    ///
+    /// * [u256] - The `u256` representation of the `U128` value.
+    ///
+    /// # Examples
+    ///
+    /// ```sway
+    /// use std::u128::U128;
+    ///
+    /// fn foo() {
+    ///    let u128_value = U128::from((18446744073709551615_u64, 18446744073709551615_u64));
+    ///    let u256_value = u256::from(u128_value);
+    /// }
+    /// ```
+    fn from(num: U128) -> Self {
+        let input = (0u64, 0u64, num.upper(), num.lower());
+        asm(input: input) {
+            input: u256
+        }
+    }
+}
+
 impl From<(u64, u64, u64, u64)> for u256 {
     /// Casts a tuple of 4 `u64` values to a `u256`.
     ///
@@ -206,6 +236,16 @@ fn test_u256_from_b256() {
     );
 }
 
+#[test]
+fn test_u256_from_u128() {
+    use ::assert::assert;
+
+    let u256_value = <u256 as From<U128>>::from(U128::from((18446744073709551615_u64, 18446744073709551615_u64)));
+    assert(
+        u256_value == 0x00000000000000000000000000000000ffffffffffffffffffffffffffffffff_u256,
+    );
+}
+
 #[test]
 fn test_u256_from_tuple() {
     use ::assert::assert;
diff --git a/sway-lib-std/src/u128.sw b/sway-lib-std/src/u128.sw
index d5c1cca2fc3..9c0f0aa28ac 100644
--- a/sway-lib-std/src/u128.sw
+++ b/sway-lib-std/src/u128.sw
@@ -3,7 +3,6 @@ library;
 
 use ::assert::assert;
 use ::convert::{From, Into};
-use ::primitive_conversions::u64::*;
 use ::flags::{disable_panic_on_overflow, set_flags};
 use ::math::*;
 use ::result::Result::{self, *};
@@ -39,7 +38,7 @@ impl From<u8> for U128 {
     fn from(val: u8) -> Self {
         Self {
             upper: 0,
-            lower: val.into(),
+            lower: val.as_u64(),
         }
     }
 }
@@ -63,7 +62,7 @@ impl From<u16> for U128 {
     fn from(val: u16) -> Self {
         Self {
             upper: 0,
-            lower: val.into(),
+            lower: val.as_u64(),
         }
     }
 }
@@ -87,7 +86,7 @@ impl From<u32> for U128 {
     fn from(val: u32) -> Self {
         Self {
             upper: 0,
-            lower: val.into(),
+            lower: val.as_u64(),
         }
     }
 }
diff --git a/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/reduced_lib.config b/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/reduced_lib.config
index 87e01ae7cd0..eee66bc33f4 100644
--- a/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/reduced_lib.config
+++ b/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/reduced_lib.config
@@ -12,6 +12,10 @@ intrinsics.sw
 constants.sw
 bytes.sw
 clone.sw
+registers.sw
+flags.sw
+math.sw
+u128.sw
 bytes_conversions.sw
 bytes_conversions/b256.sw
 bytes_conversions/u16.sw
diff --git a/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/src/lib.sw b/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/src/lib.sw
index 4f8c777cad2..0cce699db10 100644
--- a/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/src/lib.sw
+++ b/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/src/lib.sw
@@ -12,6 +12,10 @@ pub mod alloc;
 pub mod iterator;
 pub mod vec;
 pub mod bytes;
+pub mod registers;
+pub mod flags;
+pub mod math;
+pub mod u128;
 pub mod primitive_conversions;
 pub mod array_conversions;
 pub mod bytes_conversions;
diff --git a/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/src/prelude.sw b/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/src/prelude.sw
index 910663a6e90..7cbdb460de4 100644
--- a/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/src/prelude.sw
+++ b/test/src/e2e_vm_tests/reduced_std_libs/sway-lib-std-conversions/src/prelude.sw
@@ -15,6 +15,9 @@ use ::revert::{require, revert};
 // Convert
 use ::convert::From;
 
+/// U128
+use ::u128::*;
+
 // Primitive conversions
 use ::primitive_conversions::*;
 
diff --git a/test/src/e2e_vm_tests/test_programs/should_pass/test_contracts/issue_1512_repro/src/main.sw b/test/src/e2e_vm_tests/test_programs/should_pass/test_contracts/issue_1512_repro/src/main.sw
index ea39bf95f0f..a76cb9e624a 100644
--- a/test/src/e2e_vm_tests/test_programs/should_pass/test_contracts/issue_1512_repro/src/main.sw
+++ b/test/src/e2e_vm_tests/test_programs/should_pass/test_contracts/issue_1512_repro/src/main.sw
@@ -8,13 +8,13 @@ abi U128Contract {
 
 impl U128Contract for Contract {
     fn multiply_u64(a: u64, b: u64) -> (u64, u64) {
-        let result_u128: U128 = mul64(a, b);
+        let result_u128: U128Duplicate = mul64(a, b);
         (result_u128.upper, result_u128.lower)
     }
 }
 
 // U128 represented as two components of a base-(2**64) number : (upper, lower) , where value = (2**64)^upper + lower
-pub struct U128 {
+pub struct U128Duplicate {
     upper: u64,
     lower: u64,
 }
@@ -24,16 +24,16 @@ pub trait AltFrom {
 } {
 }
 
-impl core::ops::Eq for U128 {
+impl core::ops::Eq for U128Duplicate {
     fn eq(self, other: Self) -> bool {
         self.lower == other.lower && self.upper == other.upper
     }
 }
 
 /// Function for creating U128 from its u64 components
-impl AltFrom for U128 {
-    fn from(h: u64, l: u64) -> U128 {
-        U128 {
+impl AltFrom for U128Duplicate {
+    fn from(h: u64, l: u64) -> U128Duplicate {
+        U128Duplicate {
             upper: h,
             lower: l,
         }
@@ -41,16 +41,16 @@ impl AltFrom for U128 {
 }
 
 /// Methods on the U128 type
-impl U128 {
+impl U128Duplicate {
     /// Initializes a new, zeroed U128.
-    fn new() -> U128 {
-        U128 {
+    fn new() -> U128Duplicate {
+        U128Duplicate {
             upper: 0,
             lower: 0,
         }
     }
 
-    fn add(self, other: U128) -> U128 {
+    fn add(self, other: U128Duplicate) -> U128Duplicate {
         let lower = self.lower + other.lower;
         let mut upper = self.upper + other.upper;
 
@@ -62,13 +62,13 @@ impl U128 {
         // If overflow has occurred in the upper component addition, panic
         // assert(upper >= self.upper);
 
-        U128 {
+        U128Duplicate {
             upper: upper,
             lower: lower,
         }
     }
 
-    fn sub(self, other: U128) -> U128 {
+    fn sub(self, other: U128Duplicate) -> U128Duplicate {
         let mut upper = self.upper - other.upper;
         let mut lower = 0;
 
@@ -84,7 +84,7 @@ impl U128 {
         // If upper component has underflowed, panic
         // assert(upper < self.upper);
 
-        U128 {
+        U128Duplicate {
             upper: upper,
             lower: lower,
         }
@@ -94,7 +94,7 @@ impl U128 {
 }
 
 // Multiply two u64 values, producing a U128
-pub fn mul64(a: u64, b: u64) -> U128 {
+pub fn mul64(a: u64, b: u64) -> U128Duplicate {
     // Split a and b into 32-bit lo and hi components
     let a_lo = (a & 0x00000000ffffffff).try_as_u32().unwrap();
     let a_hi = (a >> 32).try_as_u32().unwrap();
@@ -122,7 +122,7 @@ pub fn mul64(a: u64, b: u64) -> U128 {
     // High result
     let result_hi: u64 = ab_hi + (ab_mid >> 32) + (ba_mid >> 32) + carry_bit;
 
-    U128 {
+    U128Duplicate {
         upper: result_hi,
         lower: result_lo,
     }