diff --git a/hw/tmp105.c b/hw/tmp105.c
index 8e8dbd9..5f41a3f 100644
--- a/hw/tmp105.c
+++ b/hw/tmp105.c
@@ -152,7 +152,7 @@ static int tmp105_tx(I2CSlave *i2c, uint8_t data)
 {
     TMP105State *s = (TMP105State *) i2c;
 
-    if (!s->len ++)
+    if (s->len == 0)
         s->pointer = data;
     else {
         if (s->len <= 2)
@@ -160,6 +160,7 @@ static int tmp105_tx(I2CSlave *i2c, uint8_t data)
         tmp105_write(s);
     }
 
+    s->len ++;
     return 0;
 }