diff --git a/modules/libcom/src/osi/os/vxWorks/osdEvent.c b/modules/libcom/src/osi/os/vxWorks/osdEvent.c
index 27b271e51..dc139432c 100644
--- a/modules/libcom/src/osi/os/vxWorks/osdEvent.c
+++ b/modules/libcom/src/osi/os/vxWorks/osdEvent.c
@@ -42,12 +42,17 @@ epicsEventStatus epicsEventWaitWithTimeout(epicsEventId id, double timeOut)
 
     if (timeOut <= 0.0) {
         ticks = 0;
-    } else if (timeOut >= (double) INT_MAX / rate) {
-        ticks = WAIT_FOREVER;
-    } else {
+    }
+    else if (timeOut < (double) INT_MAX / rate) {
         ticks = timeOut * rate;
-        if (ticks <= 0)
+        if (ticks == 0) {
+            /* 0 < timeOut < 1/rate; round up */
             ticks = 1;
+        }
+    }
+    else {
+        /* timeOut is NaN or too big to represent in ticks */
+        ticks = WAIT_FOREVER;
     }
     status = semTake((SEM_ID)id, ticks);
     if (status == OK)
diff --git a/modules/libcom/src/osi/os/vxWorks/osdMessageQueue.cpp b/modules/libcom/src/osi/os/vxWorks/osdMessageQueue.cpp
index bf27daf1b..d06952209 100644
--- a/modules/libcom/src/osi/os/vxWorks/osdMessageQueue.cpp
+++ b/modules/libcom/src/osi/os/vxWorks/osdMessageQueue.cpp
@@ -21,18 +21,28 @@ extern "C" int sysClkRateGet(void);
 LIBCOM_API int epicsStdCall epicsMessageQueueSendWithTimeout(
     epicsMessageQueueId id,
     void *message,
-    unsigned int messageSize,
+    unsigned int size,
     double timeout)
 {
     int ticks;
+    int rate = sysClkRateGet();
 
-    if (timeout<=0.0) {
+    if (timeout <= 0.0) {
         ticks = 0;
-    } else {
-        ticks = (int)(timeout*sysClkRateGet());
-        if(ticks<=0) ticks = 1;
     }
-    return msgQSend((MSG_Q_ID)id, (char *)message, messageSize, ticks, MSG_PRI_NORMAL);
+    else if (timeOut < (double) INT_MAX / rate) {
+        ticks = timeout * rate;
+        if (ticks == 0) {
+            /* 0 < timeOut < 1/rate; round up */
+            ticks = 1;
+        }
+    }
+    else {
+        /* timeOut is NaN or too big to represent in ticks */
+        ticks = WAIT_FOREVER;
+    }
+
+    return msgQSend((MSG_Q_ID)id, (char *)message, size, ticks, MSG_PRI_NORMAL);
 }
 
 LIBCOM_API int epicsStdCall epicsMessageQueueReceiveWithTimeout(
@@ -42,12 +52,22 @@ LIBCOM_API int epicsStdCall epicsMessageQueueReceiveWithTimeout(
     double timeout)
 {
     int ticks;
+    int rate = sysClkRateGet();
 
-    if (timeout<=0.0) {
+    if (timeout <= 0.0) {
         ticks = 0;
-    } else {
-        ticks = (int)(timeout*sysClkRateGet());
-        if(ticks<=0) ticks = 1;
     }
+    else if (timeOut < (double) INT_MAX / rate) {
+        ticks = timeout * rate;
+        if (ticks == 0) {
+            /* 0 < timeOut < 1/rate, round up */
+            ticks = 1;
+        }
+    }
+    else {
+        /* timeOut is NaN or too big to represent in ticks */
+        ticks = WAIT_FOREVER;
+    }
+
     return msgQReceive((MSG_Q_ID)id, (char *)message, size, ticks);
 }