diff --git a/constantine/io.nim b/constantine/io.nim
index 36c87a4..042e647 100644
--- a/constantine/io.nim
+++ b/constantine/io.nim
@@ -51,7 +51,7 @@ func fromRawUintLE(
       acc_len -= WordBitSize
       acc = src_byte shr (8 - acc_len)
 
-  if acc_len != 0:
+  if dst_idx < result.limbs.len:
     result.limbs[dst_idx] = acc
 
 func fromRawUint*(
@@ -75,9 +75,6 @@ func fromUint*(
         src: SomeUnsignedInt): T =
   ## Parse a regular unsigned integer
   ## and store it into a BigInt of size `bits`
-  static:
-    doAssert T.bits >= sizeof(src) * 8, "The BigInt bitsize (" & $T.bits &
-    ") must be greater or equal the source integer bitsize (" & $(sizeof(src) * 8) & ')'
   fromRawUint(T, cast[array[sizeof(src), byte]](src), cpuEndian)
 
 # ############################################################
diff --git a/tests/test_bigints.nim b/tests/test_bigints.nim
index f698c38..b590890 100644
--- a/tests/test_bigints.nim
+++ b/tests/test_bigints.nim
@@ -171,35 +171,34 @@ suite "Modular operations - small modulus":
 
 suite "Modular operations - small modulus - Stint specific failures highlighted by property-based testing":
   # Vectors taken from Stint - https://github.com/status-im/nim-stint
-  # We need to use hex for the modulus as we can't construct BigInt with bits < 64 from an uint64
   test "Modulo: 65696211516342324 mod 174261910798982":
     let u = 65696211516342324'u64
-    let v = "0x9e7d834a8286" # 174261910798982'u64
+    let v = 174261910798982'u64
 
     let a = BigInt[64].fromUint(u)
-    let m = BigInt[48].fromHex(v)
+    let m = BigInt[48].fromUint(v)
 
     var r: BigInt[48]
     r.reduce(a, m)
     # Copy the result in a conveniently sized buffer
-    var rr: BigInt[64]
+    var rr: BigInt[48]
     copyLimbs(rr, 0, r, 0, r.limbs.len)
 
     check:
-      bool(rr == BigInt[64].fromUint(u mod v.fromHex[:uint64]))
+      bool(rr == BigInt[48].fromUint(u mod v))
 
   test "Modulo: 15080397990160655 mod 600432699691":
     let u = 15080397990160655'u64
-    let v = "0x8bcc93e92b" # 600432699691'u64
+    let v = 600432699691'u64
 
     let a = BigInt[64].fromUint(u)
-    let m = BigInt[40].fromHex(v)
+    let m = BigInt[40].fromUint(v)
 
     var r: BigInt[40]
     r.reduce(a, m)
     # Copy the result in a conveniently sized buffer
-    var rr: BigInt[64]
+    var rr: BigInt[40]
     copyLimbs(rr, 0, r, 0, r.limbs.len)
 
     check:
-      bool(rr == BigInt[64].fromUint(u mod v.fromHex[:uint64]))
+      bool(rr == BigInt[40].fromUint(u mod v))