diff --git a/src/ncp/spinel.c b/src/ncp/spinel.c
index 5a7eb60c2..6de0542c8 100644
--- a/src/ncp/spinel.c
+++ b/src/ncp/spinel.c
@@ -2239,7 +2239,7 @@ const char *spinel_net_role_to_cstr(uint8_t net_role)
     return ret;
 }
 
-const char *spinel_mcu_power_state_to_cstr(spinel_mcu_power_state_t mcu_power_state)
+const char *spinel_mcu_power_state_to_cstr(uint8_t mcu_power_state)
 {
     const char *ret = "MCU_POWER_STATE_UNKNOWN";
 
@@ -2256,6 +2256,9 @@ const char *spinel_mcu_power_state_to_cstr(spinel_mcu_power_state_t mcu_power_st
     case SPINEL_MCU_POWER_STATE_OFF:
         ret = "MCU_POWER_STATE_OFF";
         break;
+
+    default:
+        break;
     }
 
     return ret;
diff --git a/src/ncp/spinel.h b/src/ncp/spinel.h
index f79383825..5b0757e11 100644
--- a/src/ncp/spinel.h
+++ b/src/ncp/spinel.h
@@ -4085,7 +4085,7 @@ SPINEL_API_EXTERN const char *spinel_prop_key_to_cstr(spinel_prop_key_t prop_key
 
 SPINEL_API_EXTERN const char *spinel_net_role_to_cstr(uint8_t net_role);
 
-SPINEL_API_EXTERN const char *spinel_mcu_power_state_to_cstr(spinel_mcu_power_state_t mcu_power_state);
+SPINEL_API_EXTERN const char *spinel_mcu_power_state_to_cstr(uint8_t mcu_power_state);
 
 SPINEL_API_EXTERN const char *spinel_status_to_cstr(spinel_status_t status);