diff --git a/histogram/src/atomic.rs b/histogram/src/atomic.rs
index 43384d4..c5e6e2b 100644
--- a/histogram/src/atomic.rs
+++ b/histogram/src/atomic.rs
@@ -81,6 +81,7 @@ impl AtomicHistogram {
 mod test {
     use crate::*;
 
+    #[cfg(target_pointer_width = "64")]
     #[test]
     fn size() {
         assert_eq!(std::mem::size_of::<AtomicHistogram>(), 48);
diff --git a/histogram/src/config.rs b/histogram/src/config.rs
index 9270990..37ec7c1 100644
--- a/histogram/src/config.rs
+++ b/histogram/src/config.rs
@@ -206,6 +206,7 @@ impl Config {
 mod tests {
     use super::*;
 
+    #[cfg(target_pointer_width = "64")]
     #[test]
     fn sizes() {
         assert_eq!(std::mem::size_of::<Config>(), 32);
diff --git a/histogram/src/standard.rs b/histogram/src/standard.rs
index 56aa7cc..5ee9c55 100644
--- a/histogram/src/standard.rs
+++ b/histogram/src/standard.rs
@@ -306,6 +306,7 @@ mod tests {
     use super::*;
     use rand::Rng;
 
+    #[cfg(target_pointer_width = "64")]
     #[test]
     fn size() {
         assert_eq!(std::mem::size_of::<Histogram>(), 48);