diff --git a/stdlib/3/statistics.pyi b/stdlib/3/statistics.pyi
index 966b8f3cb..f2165f0ce 100644
--- a/stdlib/3/statistics.pyi
+++ b/stdlib/3/statistics.pyi
@@ -60,6 +60,8 @@ if sys.version_info >= (3, 8):
         def inv_cdf(self, p: float) -> float: ...
         def overlap(self, other: NormalDist) -> float: ...
         def quantiles(self, n: int = ...) -> List[float]: ...
+        if sys.version_info >= (3, 9):
+            def zscore(self, x: float) -> float: ...
         def __add__(self, x2: Union[float, NormalDist]) -> NormalDist: ...
         def __sub__(self, x2: Union[float, NormalDist]) -> NormalDist: ...
         def __mul__(self, x2: float) -> NormalDist: ...