diff --git a/extensions/log/log.c b/extensions/log/log.c
index 054e198..99afc86 100644
--- a/extensions/log/log.c
+++ b/extensions/log/log.c
@@ -189,7 +189,7 @@ static void logWriteBuffer(Log *log, LogLevel level, char *buffer, short len)
 void logWrite(Log *log, LogLevel level, const char *fmt, ...)
 {
     va_list vargs;
-    short len;
+    int len;
     
 #if LOG_USING_LOCK == 1
     logLock(log);
@@ -198,6 +198,11 @@ void logWrite(Log *log, LogLevel level, const char *fmt, ...)
     len = vsnprintf(logBuffer, LOG_BUFFER_SIZE - 1, fmt, vargs);
     va_end(vargs);
 
+    if (len > LOG_BUFFER_SIZE)
+    {
+        len = LOG_BUFFER_SIZE;
+    }
+
     logWriteBuffer(log, level, logBuffer, len);
 #if LOG_USING_LOCK == 1
     logUnlock(log);
diff --git a/src/shell.c b/src/shell.c
index a73349a..fde119c 100644
--- a/src/shell.c
+++ b/src/shell.c
@@ -377,14 +377,18 @@ void shellPrint(Shell *shell, const char *fmt, ...)
 {
     char buffer[SHELL_PRINT_BUFFER];
     va_list vargs;
+    int len;
 
     SHELL_ASSERT(shell, return);
 
     va_start(vargs, fmt);
-    vsnprintf(buffer, SHELL_PRINT_BUFFER - 1, fmt, vargs);
+    len = vsnprintf(buffer, SHELL_PRINT_BUFFER, fmt, vargs);
     va_end(vargs);
-    
-    shellWriteString(shell, buffer);
+    if (len > SHELL_PRINT_BUFFER)
+    {
+        len = SHELL_PRINT_BUFFER;
+    }
+    shell->write(buffer, len);
 }
 #endif