diff --git a/Src/SerialPortVirt.c b/Src/SerialPortVirt.c
index d8c7d74..b9e735e 100644
--- a/Src/SerialPortVirt.c
+++ b/Src/SerialPortVirt.c
@@ -12,7 +12,7 @@ static uint16_t vSerialPortReceiveQueue(uint8_t *data, uint16_t size, uint32_t t
     uint16_t received = 0;
 
     uint32_t endMs = SystemGetMs() + timeout;
-    uint32_t leftMs;
+    uint32_t leftMs = 0;
 
     uint16_t granted = 0;
 
@@ -21,7 +21,13 @@ static uint16_t vSerialPortReceiveQueue(uint8_t *data, uint16_t size, uint32_t t
     }
 
     while (size && (((timeout == SystemWaitForever) || (endMs > SystemGetMs())) || (received < granted))) {
-        leftMs = endMs - SystemGetMs();
+
+        if (timeout == SystemWaitForever) {
+            leftMs = SystemWaitForever;
+        } else {
+            leftMs = endMs - SystemGetMs();
+        }
+
         if (osMessageQueueGet(queueId, data, NULL, leftMs) == osOK) {
             --size;
             ++received;