diff --git a/sim/mcuboot-sys/Cargo.toml b/sim/mcuboot-sys/Cargo.toml
index 42daf2d..ffbce48 100644
--- a/sim/mcuboot-sys/Cargo.toml
+++ b/sim/mcuboot-sys/Cargo.toml
@@ -72,6 +72,11 @@
 # image is copied to RAM before loading it.
 ram-load = []
 
+# Support simulation of direct XIP.  No swaps are performed, the image
+# is directly executed out of whichever partition contains the most
+# appropriate image.
+direct-xip = []
+
 # Check (in software) against version downgrades.
 downgrade-prevention = []
 
diff --git a/sim/mcuboot-sys/build.rs b/sim/mcuboot-sys/build.rs
index e4ceefc..f2649d3 100644
--- a/sim/mcuboot-sys/build.rs
+++ b/sim/mcuboot-sys/build.rs
@@ -31,6 +31,7 @@
     let multiimage = env::var("CARGO_FEATURE_MULTIIMAGE").is_ok();
     let downgrade_prevention = env::var("CARGO_FEATURE_DOWNGRADE_PREVENTION").is_ok();
     let ram_load = env::var("CARGO_FEATURE_RAM_LOAD").is_ok();
+    let direct_xip = env::var("CARGO_FEATURE_DIRECT_XIP").is_ok();
 
     let mut conf = cc::Build::new();
     conf.define("__BOOTSIM__", None);
@@ -64,6 +65,10 @@
         conf.define("IMAGE_EXECUTABLE_RAM_SIZE", "0x10000");
     }
 
+    if direct_xip {
+        conf.define("MCUBOOT_DIRECT_XIP", None);
+    }
+
     // Currently no more than one sig type can be used simultaneously.
     if vec![sig_rsa, sig_rsa3072, sig_ecdsa, sig_ed25519].iter()
         .fold(0, |sum, &v| sum + v as i32) > 1 {