diff --git a/cpu/arm1136/mx31/generic.c b/cpu/arm1136/mx31/generic.c
index dc031c9..1415d6c 100644
--- a/cpu/arm1136/mx31/generic.c
+++ b/cpu/arm1136/mx31/generic.c
@@ -27,8 +27,8 @@
 static u32 mx31_decode_pll(u32 reg, u32 infreq)
 {
 	u32 mfi = (reg >> 10) & 0xf;
-	u32 mfn = reg & 0x3f;
-	u32 mfd = (reg >> 16) & 0x3f;
+	u32 mfn = reg & 0x3ff;
+	u32 mfd = (reg >> 16) & 0x3ff;
 	u32 pd =  (reg >> 26) & 0xf;
 
 	mfi = mfi <= 5 ? 5 : mfi;