diff --git a/lib/std/sort/pdq.zig b/lib/std/sort/pdq.zig
index 55bd17ae93e5..da2acb2d164a 100644
--- a/lib/std/sort/pdq.zig
+++ b/lib/std/sort/pdq.zig
@@ -41,10 +41,11 @@ const Hint = enum {
 /// which each take 2 `usize` parameters indicating the index of an item.
 /// Sorts in ascending order with respect to `lessThan`.
 pub fn pdqContext(a: usize, b: usize, context: anytype) void {
+    if (a == b) return;
     // slices of up to this length get sorted using insertion sort.
     const max_insertion = 24;
     // number of allowed imbalanced partitions before switching to heap sort.
-    const max_limit = std.math.floorPowerOfTwo(usize, b - a) + 1;
+    const max_limit = math.log2_int(usize, b - a) + 1;
 
     // set upper bound on stack memory usage.
     const Range = struct { a: usize, b: usize, limit: usize };