diff --git a/lib/std/math/big/int.zig b/lib/std/math/big/int.zig
index 13ead1c421..ec79d843da 100644
--- a/lib/std/math/big/int.zig
+++ b/lib/std/math/big/int.zig
@@ -2512,7 +2512,7 @@ pub const Const = struct {
         return total_limb_lz + bits - total_limb_bits;
     }
 
-    pub fn ctz(a: Const) Limb {
+    pub fn ctz(a: Const, bits: Limb) Limb {
         // Limbs are stored in little-endian order.
         var result: Limb = 0;
         for (a.limbs) |limb| {
@@ -2520,7 +2520,7 @@ pub const Const = struct {
             result += limb_tz;
             if (limb_tz != @sizeOf(Limb) * 8) break;
         }
-        return result;
+        return @min(result, bits);
     }
 };
 
diff --git a/src/value.zig b/src/value.zig
index 89ba1fba67..62a83c7901 100644
--- a/src/value.zig
+++ b/src/value.zig
@@ -1216,10 +1216,10 @@ pub const Value = struct {
         return bigint.clz(ty.intInfo(mod).bits);
     }
 
-    pub fn ctz(val: Value, _: Type, mod: *Module) u64 {
+    pub fn ctz(val: Value, ty: Type, mod: *Module) u64 {
         var bigint_buf: BigIntSpace = undefined;
         const bigint = val.toBigInt(&bigint_buf, mod);
-        return bigint.ctz();
+        return bigint.ctz(ty.intInfo(mod).bits);
     }
 
     pub fn popCount(val: Value, ty: Type, mod: *Module) u64 {