diff --git a/semihosting/syscalls.c b/semihosting/syscalls.c
index ba28194b59..e89992cf90 100644
--- a/semihosting/syscalls.c
+++ b/semihosting/syscalls.c
@@ -253,7 +253,7 @@ static void host_open(CPUState *cs, gdb_syscall_complete_cb complete,
 {
     CPUArchState *env G_GNUC_UNUSED = cs->env_ptr;
     char *p;
-    int ret, host_flags;
+    int ret, host_flags = O_BINARY;
 
     ret = validate_lock_user_string(&p, cs, fname, fname_len);
     if (ret < 0) {
@@ -262,11 +262,11 @@ static void host_open(CPUState *cs, gdb_syscall_complete_cb complete,
     }
 
     if (gdb_flags & GDB_O_WRONLY) {
-        host_flags = O_WRONLY;
+        host_flags |= O_WRONLY;
     } else if (gdb_flags & GDB_O_RDWR) {
-        host_flags = O_RDWR;
+        host_flags |= O_RDWR;
     } else {
-        host_flags = O_RDONLY;
+        host_flags |= O_RDONLY;
     }
     if (gdb_flags & GDB_O_CREAT) {
         host_flags |= O_CREAT;