diff --git a/kernel/chips/ds1621.c b/kernel/chips/ds1621.c
index f0164669..b69cd968 100644
--- a/kernel/chips/ds1621.c
+++ b/kernel/chips/ds1621.c
@@ -183,7 +183,8 @@ int ds1621_detect(struct i2c_adapter *adapter, int address,
 #endif
 
 	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
-				     I2C_FUNC_SMBUS_WORD_DATA))
+				     I2C_FUNC_SMBUS_WORD_DATA |
+				     I2C_FUNC_SMBUS_WRITE_BYTE))
 		    goto ERROR0;
 
 	/* OK. For now, we presume we have a valid client. We now create the
diff --git a/kernel/chips/pcf8591.c b/kernel/chips/pcf8591.c
index 383fa2bf..8e63befa 100644
--- a/kernel/chips/pcf8591.c
+++ b/kernel/chips/pcf8591.c
@@ -179,7 +179,8 @@ int pcf8591_detect(struct i2c_adapter *adapter, int address,
         }
 #endif
 
-        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE))
+        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE
+                                     | I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
                 goto ERROR0;
 
         /* OK. For now, we presume we have a valid client. We now create the