diff --git a/rtl837x_sfr.h b/rtl837x_sfr.h
index f3e4a72..45c117a 100644
--- a/rtl837x_sfr.h
+++ b/rtl837x_sfr.h
@@ -5,8 +5,13 @@ __sfr16 __at(0xa2a3) SFR_REG_ADDR_U16;
 __sfr __at(0xa2) SFR_REG_ADDRH;
 __sfr __at(0xa3) SFR_REG_ADDRL;
 __sfr16 __at(0xa6a7) SFR_DATA_U16;
-__sfr32 __at(0xa4a5a6a7) SFR_DATA_U32;
-__sfr32 __at(0xa7a6a5a4) SFR_DATA_U32LE;
+// Disabling until the SDCC bug #4070 is fixed.
+// Generate wrong address for `a4` location.
+// Both read from and write to `SFR_DATA_U32`.
+// __sfr32 __at(0xa4a5a6a7) SFR_DATA_U32;
+// __sfr32 __at(0xa7a6a5a4) SFR_DATA_U32LE;
+// This is the upper part of the U32 as a workaround for SDCC bug #4070.
+__sfr16 __at(0xa4a5) SFR_DATA_U16_UPPER;
 __sfr __at(0xa4) SFR_DATA_24;
 __sfr __at(0xa5) SFR_DATA_16;
 __sfr __at(0xa6) SFR_DATA_8;