diff --git a/sim/mcuboot-sys/src/api.rs b/sim/mcuboot-sys/src/api.rs
index 8f8b7be..7bd4fc4 100644
--- a/sim/mcuboot-sys/src/api.rs
+++ b/sim/mcuboot-sys/src/api.rs
@@ -46,6 +46,16 @@
     }
 }
 
+impl Default for FlashContext {
+    fn default() -> FlashContext {
+        FlashContext {
+            flash_map: HashMap::new(),
+            flash_params: HashMap::new(),
+            flash_areas: CAreaDescPtr{ptr: ptr::null()},
+        }
+    }
+}
+
 #[repr(C)]
 #[derive(Debug, Default)]
 pub struct CSimContext {
@@ -71,6 +81,14 @@
     }
 }
 
+impl Default for CSimContextPtr {
+    fn default() -> CSimContextPtr {
+        CSimContextPtr {
+            ptr: ptr::null(),
+        }
+    }
+}
+
 thread_local! {
     pub static THREAD_CTX: RefCell<FlashContext> = RefCell::new(FlashContext::new());
     pub static SIM_CTX: RefCell<CSimContextPtr> = RefCell::new(CSimContextPtr::new());