diff --git a/hw/tmp105.c b/hw/tmp105.c
index 0ade4eb6bd9766d7d0fffff3d14747e8c2971e36..10d94c903ca4208773606bac5749fc2a7e677219 100644
--- a/hw/tmp105.c
+++ b/hw/tmp105.c
@@ -153,11 +153,14 @@ 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)
+        s->len++;
+    } else {
+        if (s->len <= 2) {
             s->buf[s->len - 1] = data;
+        }
+        s->len++;
         tmp105_write(s);
     }