diff --git a/beacon_node/src/main.rs b/beacon_node/src/main.rs
index 54e4529c40..bb88e8f929 100644
--- a/beacon_node/src/main.rs
+++ b/beacon_node/src/main.rs
@@ -357,6 +357,14 @@ fn main() {
 
     let log = slog::Logger::root(drain.fuse(), o!());
 
+    if std::mem::size_of::<usize>() != 8 {
+        crit!(
+            log,
+            "Lighthouse only supports 64bit CPUs";
+            "detected" => format!("{}bit", std::mem::size_of::<usize>() * 8)
+        );
+    }
+
     warn!(
         log,
         "Ethereum 2.0 is pre-release. This software is experimental."
diff --git a/validator_client/src/main.rs b/validator_client/src/main.rs
index e445218ebd..58914a9a81 100644
--- a/validator_client/src/main.rs
+++ b/validator_client/src/main.rs
@@ -157,6 +157,14 @@ fn main() {
 
     let mut log = slog::Logger::root(drain.fuse(), o!());
 
+    if std::mem::size_of::<usize>() != 8 {
+        crit!(
+            log,
+            "Lighthouse only supports 64bit CPUs";
+            "detected" => format!("{}bit", std::mem::size_of::<usize>() * 8)
+        );
+    }
+
     let (client_config, eth2_config) = match get_configs(&matches, &mut log) {
         Ok(tuple) => tuple,
         Err(e) => {