diff --git a/edify/expr.h b/edify/expr.h
index 36f8e96..5c06de8 100644
--- a/edify/expr.h
+++ b/edify/expr.h
@@ -19,6 +19,7 @@
 
 #include <unistd.h>
 
+#include "error_code.h"
 #include "yydefs.h"
 
 #define MAX_STRING_LEN 1024
@@ -39,6 +40,15 @@
     // Should be NULL initially, will be either NULL or a malloc'd
     // pointer after Evaluate() returns.
     char* errmsg;
+
+    // error code indicates the type of failure (e.g. failure to update system image)
+    // during the OTA process.
+    ErrorCode error_code = kNoError;
+
+    // cause code provides more detailed reason of an OTA failure (e.g. fsync error)
+    // in addition to the error code.
+    CauseCode cause_code = kNoCause;
+
 } State;
 
 #define VAL_STRING  1  // data will be NULL-terminated; size doesn't count null
@@ -152,7 +162,13 @@
 
 // Use printf-style arguments to compose an error message to put into
 // *state.  Returns NULL.
-Value* ErrorAbort(State* state, const char* format, ...) __attribute__((format(printf, 2, 3)));
+Value* ErrorAbort(State* state, const char* format, ...)
+    __attribute__((format(printf, 2, 3), deprecated));
+
+// ErrorAbort has an optional (but recommended) argument 'cause_code'. If the cause code
+// is set, it will be logged into last_install and provides reason of OTA failures.
+Value* ErrorAbort(State* state, CauseCode cause_code, const char* format, ...)
+    __attribute__((format(printf, 3, 4)));
 
 // Wrap a string into a Value, taking ownership of the string.
 Value* StringValue(char* str);