diff --git a/rpcsx-os/backtrace.cpp b/rpcsx-os/backtrace.cpp
index 7b8d33df5..a6e8ad5c8 100644
--- a/rpcsx-os/backtrace.cpp
+++ b/rpcsx-os/backtrace.cpp
@@ -77,11 +77,12 @@ void rx::printStackTrace(ucontext_t *context, orbis::Thread *thread,
   unw_cursor_t cursor;
 
   char buffer[1024];
-
+  flockfile(stderr);
   if (int r = unw_init_local2(&cursor, context, UNW_INIT_SIGNAL_FRAME)) {
     int len = snprintf(buffer, sizeof(buffer), "unw_init_local: %s\n",
                        unw_strerror(r));
     write(fileno, buffer, len);
+    funlockfile(stderr);
     return;
   }
 
@@ -123,4 +124,5 @@ void rx::printStackTrace(ucontext_t *context, orbis::Thread *thread,
     write(fileno, buffer, offset);
     count++;
   } while (unw_step(&cursor) > 0 && count < 32);
+  funlockfile(stderr);
 }
diff --git a/rpcsx-os/main.cpp b/rpcsx-os/main.cpp
index 475bc195f..70a30d255 100644
--- a/rpcsx-os/main.cpp
+++ b/rpcsx-os/main.cpp
@@ -178,6 +178,7 @@ static void onSysEnter(orbis::Thread *thread, int id, uint64_t *args,
   if (true || !g_traceSyscalls) {
     return;
   }
+  flockfile(stdout);
   std::printf("   [%u] ", thread->tid);
 
   if (auto name = getSyscallName(thread, id)) {
@@ -195,6 +196,7 @@ static void onSysEnter(orbis::Thread *thread, int id, uint64_t *args,
   }
 
   std::printf(")\n");
+  funlockfile(stdout);
 }
 
 static void onSysExit(orbis::Thread *thread, int id, uint64_t *args,
@@ -203,6 +205,7 @@ static void onSysExit(orbis::Thread *thread, int id, uint64_t *args,
     return;
   }
 
+  flockfile(stdout);
   std::printf("%c: [%u] ", result.isError() ? 'E' : 'S', thread->tid);
 
   if (auto name = getSyscallName(thread, id)) {
@@ -221,6 +224,7 @@ static void onSysExit(orbis::Thread *thread, int id, uint64_t *args,
 
   std::printf(") -> Status %d, Value %lx:%lx\n", result.value(),
               thread->retval[0], thread->retval[1]);
+  funlockfile(stdout);
 }
 
 static int ps4Exec(orbis::Process *mainProcess,