diff --git a/src/mesa/drivers/dri/r300/radeon_screen.c b/src/mesa/drivers/dri/r300/radeon_screen.c
index c6c52c11df1..aab5ac425fd 100644
--- a/src/mesa/drivers/dri/r300/radeon_screen.c
+++ b/src/mesa/drivers/dri/r300/radeon_screen.c
@@ -203,6 +203,7 @@ static const struct dri_debug_control debug_control[] = {
 #define PCI_CHIP_R300_NF		0x4E46
 #define PCI_CHIP_R300_NG		0x4E47
 #define PCI_CHIP_R350_NH                0x4E48
+#define PCI_CHIP_R420_JK                0x4a4b
 #endif
 
 #ifdef USE_NEW_INTERFACE
@@ -382,6 +383,10 @@ static radeonScreenPtr radeonCreateScreen(__DRIscreenPrivate * sPriv)
 		screen->chipset = RADEON_CHIP_R300;
 		break;
 
+	case PCI_CHIP_R420_JK:
+		screen->chipset = RADEON_CHIP_R420;
+		break;
+
 	default:
 		fprintf(stderr,
 			"Unknown device ID %04X, please report. Assuming plain R300.\n",
diff --git a/src/mesa/drivers/dri/r300/radeon_screen.h b/src/mesa/drivers/dri/r300/radeon_screen.h
index a1a019162ab..ac8471feaa3 100644
--- a/src/mesa/drivers/dri/r300/radeon_screen.h
+++ b/src/mesa/drivers/dri/r300/radeon_screen.h
@@ -54,6 +54,7 @@ typedef struct {
 #define RADEON_CHIP_REAL_R200		1
 #define RADEON_CHIP_R300		2
 #define RADEON_CHIP_RV350		3
+#define RADEON_CHIP_R420		4
 #define RADEON_CHIP_MASK		0x0f
 
 #define RADEON_CHIPSET_TCL		(1 << 8)