diff --git a/org.fortiss.af3.platform.raspberry/trunk/lib/src/LaserRangeFinder.c b/org.fortiss.af3.platform.raspberry/trunk/lib/src/LaserRangeFinder.c
index 93eb8c417a348a05a3a046db97adc471e3854258..87c80295fc864c2b2e7daecde40f23b6986b04fd 100644
--- a/org.fortiss.af3.platform.raspberry/trunk/lib/src/LaserRangeFinder.c
+++ b/org.fortiss.af3.platform.raspberry/trunk/lib/src/LaserRangeFinder.c
@@ -88,9 +88,15 @@ GEN_TYPE_int lrf_read() {
                 }
             } else {
                 d = atoi(value);
-                printf("%d\n",d);
-                timeout = 0;
-                return d;
+                if (d != 0) {
+                    printf("%d\n", d);
+                    timeout = 0;
+                    return d;
+                } else {
+                    timeout++;
+                    printf("-1: zero value\n");
+                    return -1;
+                }
             }
         }
     }