diff --git a/tool/microkit/src/sel4.rs b/tool/microkit/src/sel4.rs
index 5a566bd96..bbeddecee 100644
--- a/tool/microkit/src/sel4.rs
+++ b/tool/microkit/src/sel4.rs
@@ -295,7 +295,7 @@ pub struct Config {
     pub fpu: bool,
     /// ARM-specific, number of physical address bits
     pub arm_pa_size_bits: Option<usize>,
-    /// ARM-specific, where or not SMC forwarding is allowed
+    /// ARM-specific, whether or not SMC forwarding is allowed
     /// False if the kernel config option has not been enabled.
     /// None on any non-ARM architecture.
     pub arm_smc: Option<bool>,