diff --git a/V203/hello/linux/print.cpp b/V203/hello/linux/print.cpp
index 66bba97..a97c2e1 100644
--- a/V203/hello/linux/print.cpp
+++ b/V203/hello/linux/print.cpp
@@ -1,16 +1,22 @@
 #include <cstdio>
+#include <mutex>
 #include "utils.h"
+static std::mutex Mutex;
+
 void print_morse_table (const TABLE<unsigned char, 64> & tab) {
+  Mutex.lock();
   int n = 0;
   printf("static const unsigned char compressed_table [] = {");
   for (auto & e: tab) {
-    if ((n % 16) == 0) printf("\n");
+    if ((n % 16) == 0) printf("\n  ");
     printf("0x%02x,", e);
     n++;
   }
   printf("\n};\n");
+  Mutex.unlock();
 }
 void print_sinus_table (const TABLE<unsigned short, 256> & tab) {
+  Mutex.lock();
   int n = 0;
   printf("static const uint16_t sin_tab [] = {");
   for (auto & e: tab) {
@@ -19,4 +25,5 @@ void print_sinus_table (const TABLE<unsigned short, 256> & tab) {
     n++;
   }
   printf("\n};\n");
+  Mutex.unlock();
 }