diff --git a/src/mame/drivers/astrof.c b/src/mame/drivers/astrof.c
index 6b188e94450..5ad68a9e6cd 100644
--- a/src/mame/drivers/astrof.c
+++ b/src/mame/drivers/astrof.c
@@ -192,7 +192,7 @@ rgb_t astrof_state::make_pen( UINT8 data )
 }
 
 
-void astrof_state::astrof_get_pens( rgb_t *pens )
+void astrof_state::astrof_get_pens( pen_t *pens )
 {
 	offs_t i;
 	UINT8 bank = (m_astrof_palette_bank ? 0x10 : 0x00);
@@ -228,7 +228,7 @@ void astrof_state::astrof_get_pens( rgb_t *pens )
 }
 
 
-void astrof_state::tomahawk_get_pens( rgb_t *pens )
+void astrof_state::tomahawk_get_pens( pen_t *pens )
 {
 	offs_t i;
 	UINT8 *prom = memregion("proms")->base();
@@ -352,7 +352,7 @@ WRITE8_MEMBER(astrof_state::tomahawk_video_control_2_w)
 }
 
 
-void astrof_state::video_update_common( bitmap_rgb32 &bitmap, const rectangle &cliprect, rgb_t *pens )
+void astrof_state::video_update_common( bitmap_rgb32 &bitmap, const rectangle &cliprect, pen_t *pens, int num_pens )
 {
 	offs_t offs;
 
@@ -363,8 +363,8 @@ void astrof_state::video_update_common( bitmap_rgb32 &bitmap, const rectangle &c
 
 		UINT8 color = m_colorram[offs >> 1];
 
-		rgb_t back_pen = pens[color | 0x00];
-		rgb_t fore_pen = pens[color | 0x01];
+		pen_t back_pen = pens[(color & (num_pens-1)) | 0x00];
+		pen_t fore_pen = pens[(color & (num_pens-1)) | 0x01];
 
 		UINT8 y = offs;
 		UINT8 x = offs >> 8 << 3;
@@ -382,7 +382,7 @@ void astrof_state::video_update_common( bitmap_rgb32 &bitmap, const rectangle &c
 
 		for (i = 0; i < 8; i++)
 		{
-			rgb_t pen = (data & 0x01) ? fore_pen : back_pen;
+			pen_t pen = (data & 0x01) ? fore_pen : back_pen;
 
 			if (m_flipscreen)
 				bitmap.pix32(y, 255 - x) = pen;
@@ -398,11 +398,11 @@ void astrof_state::video_update_common( bitmap_rgb32 &bitmap, const rectangle &c
 
 UINT32 astrof_state::screen_update_astrof(screen_device &screen, bitmap_rgb32 &bitmap, const rectangle &cliprect)
 {
-	rgb_t pens[ASTROF_NUM_PENS];
+	pen_t pens[ASTROF_NUM_PENS];
 
 	astrof_get_pens(pens);
 
-	video_update_common(bitmap, cliprect, pens);
+	video_update_common(bitmap, cliprect, pens, ASTROF_NUM_PENS);
 
 	return 0;
 }
@@ -410,11 +410,11 @@ UINT32 astrof_state::screen_update_astrof(screen_device &screen, bitmap_rgb32 &b
 
 UINT32 astrof_state::screen_update_tomahawk(screen_device &screen, bitmap_rgb32 &bitmap, const rectangle &cliprect)
 {
-	rgb_t pens[TOMAHAWK_NUM_PENS];
+	pen_t pens[TOMAHAWK_NUM_PENS];
 
 	tomahawk_get_pens(pens);
 
-	video_update_common(bitmap, cliprect, pens);
+	video_update_common(bitmap, cliprect, pens, TOMAHAWK_NUM_PENS);
 
 	return 0;
 }
diff --git a/src/mame/includes/astrof.h b/src/mame/includes/astrof.h
index 9fbd5108272..e613dff8e31 100644
--- a/src/mame/includes/astrof.h
+++ b/src/mame/includes/astrof.h
@@ -79,12 +79,12 @@ public:
 	UINT32 screen_update_tomahawk(screen_device &screen, bitmap_rgb32 &bitmap, const rectangle &cliprect);
 	TIMER_DEVICE_CALLBACK_MEMBER(irq_callback);
 	rgb_t make_pen( UINT8 data );
-	void astrof_get_pens( rgb_t *pens );
-	void tomahawk_get_pens( rgb_t *pens );
+	void astrof_get_pens( pen_t *pens );
+	void tomahawk_get_pens( pen_t *pens );
 	void astrof_set_video_control_2( UINT8 data );
 	void spfghmk2_set_video_control_2( UINT8 data );
 	void tomahawk_set_video_control_2( UINT8 data );
-	void video_update_common( bitmap_rgb32 &bitmap, const rectangle &cliprect, rgb_t *pens );
+	void video_update_common( bitmap_rgb32 &bitmap, const rectangle &cliprect, pen_t *pens, int num_pens );
 };
 
 /*----------- defined in audio/astrof.c -----------*/