diff --git a/libubb/include/ubb/mmcclk.h b/libubb/include/ubb/mmcclk.h
index 289a887..8762e90 100644
--- a/libubb/include/ubb/mmcclk.h
+++ b/libubb/include/ubb/mmcclk.h
@@ -16,7 +16,7 @@
 #include <stdint.h>
 
 
-#define	BEN_SYS_CLK_HZ		336000000
+#define	BEN_PLL_CLK_HZ		336000000
 
 
 struct mmcclk {
diff --git a/libubb/mmcclk.c b/libubb/mmcclk.c
index b84fe59..42202d7 100644
--- a/libubb/mmcclk.c
+++ b/libubb/mmcclk.c
@@ -30,7 +30,11 @@ static int calculate_clock(struct mmcclk *dsc)
 
 void mmcclk_first(struct mmcclk *dsc, int sys_clk_hz)
 {
-	dsc->sys_clk_hz = sys_clk_hz ? sys_clk_hz : BEN_SYS_CLK_HZ;
+	if (sys_clk_hz)
+		dsc->sys_clk_hz = sys_clk_hz;
+	else
+		dsc->sys_clk_hz =
+		    (CPCCR >> 21) & 1 ? BEN_PLL_CLK_HZ : BEN_PLL_CLK_HZ/2;
 	dsc->clkdiv = dsc->clkrt = 0;
 	if (calculate_clock(dsc))
 		return;