diff --git a/sim/mcuboot-sys/src/api.rs b/sim/mcuboot-sys/src/api.rs
index 7014d5c..0a098ff 100644
--- a/sim/mcuboot-sys/src/api.rs
+++ b/sim/mcuboot-sys/src/api.rs
@@ -90,7 +90,7 @@
 }
 
 #[repr(C)]
-#[derive(Debug, Default)]
+#[derive(Debug)]
 pub struct CSimContext {
     pub flash_counter: libc::c_int,
     pub jumped: libc::c_int,
@@ -99,7 +99,19 @@
     // NOTE: Always leave boot_jmpbuf declaration at the end; this should
     // store a "jmp_buf" which is arch specific and not defined by libc crate.
     // The size below is enough to store data on a x86_64 machine.
-    pub boot_jmpbuf: [u64; 16],
+    pub boot_jmpbuf: [u64; 48],
+}
+
+impl Default for CSimContext {
+    fn default() -> Self {
+        CSimContext {
+            flash_counter: 0,
+            jumped: 0,
+            c_asserts: 0,
+            c_catch_asserts: 0,
+            boot_jmpbuf: [0; 48],
+        }
+    }
 }
 
 pub struct CSimContextPtr {
diff --git a/sim/mcuboot-sys/src/c.rs b/sim/mcuboot-sys/src/c.rs
index 284cac0..9d2a321 100644
--- a/sim/mcuboot-sys/src/c.rs
+++ b/sim/mcuboot-sys/src/c.rs
@@ -81,10 +81,8 @@
             None => 0,
             Some(ref c) => **c as libc::c_int
         },
-        jumped: 0,
-        c_asserts: 0,
         c_catch_asserts: if catch_asserts { 1 } else { 0 },
-        boot_jmpbuf: [0; 16],
+        .. Default::default()
     };
     let mut rsp = api::BootRsp {
         br_hdr: std::ptr::null(),