diff --git a/drivers/isl29020/isl29020.c b/drivers/isl29020/isl29020.c
index f687039c2a77fdb16f48cb8613e7ef006a373fbb..f0a0a4f93dba3f8cf9e13f118804ff472c5deb2c 100644
--- a/drivers/isl29020/isl29020.c
+++ b/drivers/isl29020/isl29020.c
@@ -57,13 +57,14 @@ int isl29020_read(isl29020_t *dev)
 {
     char low, high;
     uint16_t res;
+    int ret;
 
     i2c_acquire(dev->i2c);
     /* read lighting value */
-    res = i2c_read_reg(dev->i2c, dev->address, ISL29020_REG_LDATA, &low);
-    res += i2c_read_reg(dev->i2c, dev->address, ISL29020_REG_HDATA, &high);
+    ret = i2c_read_reg(dev->i2c, dev->address, ISL29020_REG_LDATA, &low);
+    ret += i2c_read_reg(dev->i2c, dev->address, ISL29020_REG_HDATA, &high);
     i2c_release(dev->i2c);
-    if (res < 2) {
+    if (ret < 2) {
         return -1;
     }
     res = (high << 8) | low;