diff --git a/drivers/unix/os_unix.cpp b/drivers/unix/os_unix.cpp
index 1d94b9618d1..27203b3eed7 100644
--- a/drivers/unix/os_unix.cpp
+++ b/drivers/unix/os_unix.cpp
@@ -307,7 +307,7 @@ Error OS_Unix::execute(const String &p_path, const List<String> &p_arguments, bo
 			if (p_pipe_mutex) {
 				p_pipe_mutex->lock();
 			}
-			(*r_pipe) += buf;
+			(*r_pipe) += String::utf8(buf);
 			if (p_pipe_mutex) {
 				p_pipe_mutex->unlock();
 			}
diff --git a/platform/windows/os_windows.cpp b/platform/windows/os_windows.cpp
index 7f4392c624a..6757f60a062 100644
--- a/platform/windows/os_windows.cpp
+++ b/platform/windows/os_windows.cpp
@@ -2724,7 +2724,7 @@ Error OS_Windows::execute(const String &p_path, const List<String> &p_arguments,
 			if (p_pipe_mutex) {
 				p_pipe_mutex->lock();
 			}
-			(*r_pipe) += buf;
+			(*r_pipe) += String::utf8(buf);
 			if (p_pipe_mutex) {
 				p_pipe_mutex->unlock();
 			}