diff --git a/Standard/src/Convert/Convert.qs b/Standard/src/Convert/Convert.qs
index b69b24bd51d..85a89b88367 100644
--- a/Standard/src/Convert/Convert.qs
+++ b/Standard/src/Convert/Convert.qs
@@ -76,8 +76,10 @@ namespace Microsoft.Quantum.Convert {
     /// An array of boolean values representing `number`.
     ///
     /// # Remarks
-    /// The input `number` must be at most $2^{\texttt{bits}} - 1$.
+    /// The input `bits` must be between 0 and 63.
+    /// The input `number` must be between 0 and $2^{\texttt{bits}} - 1$.
     function IntAsBoolArray(number : Int, bits : Int) : Bool[] {
+        Fact(bits >= 0 and bits <= 63, $"`bits` must be between 0 and 63 {2^bits}");
         EqualityFactB(number >= 0 and number < 2 ^ bits, true, $"`number` must be between 0 and 2^`bits` - 1");
         mutable outputBits = new Bool[bits];
         mutable tempInt = number;