diff --git a/src/ast_2dtool.h b/src/ast_2dtool.h
index c3cc54a..71632af 100644
--- a/src/ast_2dtool.h
+++ b/src/ast_2dtool.h
@@ -20,6 +20,9 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
+#ifndef AST_2DTOOL_H
+#define AST_2DTOOL_H
+
 /* Eng Capability Definition */
 #define	ENG_CAP_Sync				0x0001
 #define	ENG_CAP_ScreenToScreenCopy		0x0002
@@ -623,3 +626,5 @@ typedef struct {
       }
 
 Bool bASTGetLineTerm(_LINEInfo *LineInfo, LINEPARAM *dsLineParam);
+
+#endif /* AST_2DTOOL_H */
diff --git a/src/ast_cursor.h b/src/ast_cursor.h
index d4de479..a3d27d2 100644
--- a/src/ast_cursor.h
+++ b/src/ast_cursor.h
@@ -20,6 +20,9 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
+#ifndef AST_CURSOR_H
+#define AST_CURSOR_H
+
 #define	MAX_HWC_WIDTH		64
 #define	MAX_HWC_HEIGHT		64
 #define HWC_SIZE		(MAX_HWC_WIDTH*MAX_HWC_HEIGHT*2)
@@ -37,3 +40,5 @@
 #define HWC_SIGNATURE_Y         0x10
 #define HWC_SIGNATURE_HOTSPOTX  0x14
 #define HWC_SIGNATURE_HOTSPOTY  0x18
+
+#endif /* AST_CURSOR_H */
diff --git a/src/ast_mode.h b/src/ast_mode.h
index a054100..82b3cfc 100644
--- a/src/ast_mode.h
+++ b/src/ast_mode.h
@@ -20,6 +20,9 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
+#ifndef AST_MODE_H
+#define AST_MODE_H
+
 /* Mode Limitation */
 #define MAX_HResolution		1920
 #define MAX_VResolution		1200
@@ -132,3 +135,5 @@ typedef struct {
     PVBIOS_ENHTABLE_STRUCT pEnhTableEntry;
 
 } VBIOS_MODE_INFO, *PVBIOS_MODE_INFO;
+
+#endif /* AST_MODE_H */
diff --git a/src/ast_vgatool.h b/src/ast_vgatool.h
index f9b65ba..fc23ef1 100644
--- a/src/ast_vgatool.h
+++ b/src/ast_vgatool.h
@@ -20,6 +20,9 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
+#ifndef AST_VGATOOL_H
+#define AST_VGATOOL_H
+
 /* VRAM Size Definition */
 #define VIDEOMEM_SIZE_08M	0x00800000
 #define VIDEOMEM_SIZE_16M	0x01000000
@@ -170,3 +173,5 @@
 /* Delay */
 #define DelayUS(x)		usleep(x)
 #define DelayMS(x)		DelayUS(1000*x)
+
+#endif /* AST_VGATOOL_H */