diff --git a/juno_samples/rodinia/cfd/src/main.rs b/juno_samples/rodinia/cfd/src/main.rs
index 83db67d833fe27a6be09ebe8367f7eedf9f41fed..9a51ddfafefb2c525410b87752be6822b611d167 100644
--- a/juno_samples/rodinia/cfd/src/main.rs
+++ b/juno_samples/rodinia/cfd/src/main.rs
@@ -146,6 +146,8 @@ fn cfd_harness(args: CFDInputs) {
         pre_euler,
     } = args;
 
+    assert!(block_size % 8 == 0, "Hercules expects all arrays to be 32-byte aligned, cfd uses structs of arrays that are annoying to deal with if the block_size is not a multiple of 8");
+
     let FarFieldConditions {
         ff_variable,
         ff_fc_momentum_x,