diff --git a/core/error.c b/core/error.c
index 3e7613b..fdd7acc 100644
--- a/core/error.c
+++ b/core/error.c
@@ -725,7 +725,7 @@ static const struct b_error_msg builtin_msg[] = {
 	B_ERROR_MSG_TEMPLATE(
 		B_MSG_CLASS_SPECIFIES_UNKNOWN_INTERFACE,
 		"Class @[class_name] specifies an implementation for interface "
-                "@[interface_name] that it does not extend or inherit",
+		"@[interface_name] that it does not extend or inherit",
 		B_ERROR_TEMPLATE_PARAM(
 			"class_name", B_ERROR_TEMPLATE_PARAM_STRING, "%s"),
 		B_ERROR_TEMPLATE_PARAM(
diff --git a/core/error.h b/core/error.h
index 050fd72..19abae5 100644
--- a/core/error.h
+++ b/core/error.h
@@ -2,6 +2,7 @@
 #define _BLUELIB_ERROR_H_
 
 #include <blue/core/error.h>
+#include <blue/core/queue.h>
 
 struct b_error_stack_frame {
 	b_queue_entry f_entry;
diff --git a/core/include/blue/core/error.h b/core/include/blue/core/error.h
index 42b3fbc..e02281b 100644
--- a/core/include/blue/core/error.h
+++ b/core/include/blue/core/error.h
@@ -2,9 +2,9 @@
 #define BLUE_CORE_ERROR_H_
 
 #include <blue/core/misc.h>
-#include <blue/core/queue.h>
 #include <blue/core/status.h>
 #include <stdarg.h>
+#include <stdbool.h>
 
 #define B_ERROR_TEMPLATE_PARAMETER_MAX 4
 #define B_ERROR_MSG_ID_INVALID         ((unsigned long)-1)