diff --git a/src/ADCSensor.cpp b/src/ADCSensor.cpp
index 4aa8cc1..330de52 100644
--- a/src/ADCSensor.cpp
+++ b/src/ADCSensor.cpp
@@ -176,7 +176,7 @@
         (*bridgeGpio).set(0);
     }
     int fd = open(path.c_str(), O_RDONLY);
-    if (fd <= 0)
+    if (fd < 0)
     {
         return; // we're no longer valid
     }