diff --git a/src/moments/variance0.rs b/src/moments/variance0.rs
index b158026..f0daeba 100644
--- a/src/moments/variance0.rs
+++ b/src/moments/variance0.rs
@@ -83,7 +83,7 @@ impl Variance0 {
     /// This is an unbiased estimator of the variance of the population.
     #[inline]
     pub fn sample_variance(&self) -> f64 {
-        if self.avg.len() < 1 + ddof as usize {
+        if self.avg.len() < 1 + ddof as u64 {
             return 0.;
         }
         self.sum_2 / f64::approx_from(self.avg.len() - ddof).unwrap()
@@ -95,7 +95,7 @@ impl Variance0 {
     #[inline]
     pub fn population_variance(&self) -> f64 {
         let n = self.avg.len();
-        if n < 1 + ddof as usize {
+        if n < 1 + ddof as u64 {
             return 0.;
         }
         self.sum_2 / f64::approx_from(n).unwrap()
diff --git a/src/moments/variance1.rs b/src/moments/variance1.rs
index 0dc4304..5b2d8e6 100644
--- a/src/moments/variance1.rs
+++ b/src/moments/variance1.rs
@@ -83,7 +83,7 @@ impl Variance1 {
     /// This is an unbiased estimator of the variance of the population.
     #[inline]
     pub fn sample_variance(&self) -> f64 {
-        if self.avg.len() < 1 + ddof as usize {
+        if self.avg.len() < 1 + ddof as u64 {
             return 0.;
         }
         self.sum_2 / f64::approx_from(self.avg.len() - ddof).unwrap()
@@ -95,7 +95,7 @@ impl Variance1 {
     #[inline]
     pub fn population_variance(&self) -> f64 {
         let n = self.avg.len();
-        if n < 1 + ddof as usize {
+        if n < 1 + ddof as u64 {
             return 0.;
         }
         self.sum_2 / f64::approx_from(n).unwrap()