diff --git a/libraries/AP_Generator/AP_Generator_IE_FuelCell.cpp b/libraries/AP_Generator/AP_Generator_IE_FuelCell.cpp
index 21725b932c251..7a13bed22e574 100644
--- a/libraries/AP_Generator/AP_Generator_IE_FuelCell.cpp
+++ b/libraries/AP_Generator/AP_Generator_IE_FuelCell.cpp
@@ -43,11 +43,9 @@ void AP_Generator_IE_FuelCell::update()
     const uint32_t now = AP_HAL::millis();
 
    // Read any available data
-    uint32_t nbytes = MIN(_uart->available(),30u);
-    while (nbytes-- > 0) {
-        const int16_t c = _uart->read();
-        if (c < 0) {
-            // Nothing to decode
+    for (uint8_t i=0; i<30; i++) {  // process at most n bytes
+        uint8_t c;
+        if (!_uart->read(c)) {
             break;
         }