diff --git a/apps/codecs.c b/apps/codecs.c
index 4d97baacbe..46d9223560 100644
--- a/apps/codecs.c
+++ b/apps/codecs.c
@@ -83,7 +83,7 @@ static int open(const char* pathname, int flags, ...)
     {
         va_list ap;
         va_start(ap, flags);
-        fd = sim_open(pathname, flags, va_arg(ap, mode_t));
+        fd = sim_open(pathname, flags, va_arg(ap, unsigned int));
         va_end(ap);
     }
     else
diff --git a/apps/plugin.c b/apps/plugin.c
index 8a32a159b4..e4480deed1 100644
--- a/apps/plugin.c
+++ b/apps/plugin.c
@@ -987,8 +987,7 @@ static int open_wrapper(const char* pathname, int flags, ...)
     {
         va_list ap;
         va_start(ap, flags);
-        int fd;
-        fd = sim_open(pathname, flags, va_arg(ap, mode_t));
+        fd = sim_open(pathname, flags, va_arg(ap, unsigned int));
         va_end(ap);
     }
     else
diff --git a/apps/plugins/doom/rockdoom.c b/apps/plugins/doom/rockdoom.c
index 1383a2b520..26afdd93db 100644
--- a/apps/plugins/doom/rockdoom.c
+++ b/apps/plugins/doom/rockdoom.c
@@ -72,7 +72,7 @@ int my_open(const char *file, int flags, ...)
    {
       va_list ap;
       va_start(ap, flags);
-      filearray[fpoint]=rb->open(file, flags, va_arg(ap, mode_t));
+      filearray[fpoint]=rb->open(file, flags, va_arg(ap, unsigned int));
       va_end(ap);
    }
    else
diff --git a/uisimulator/common/io.c b/uisimulator/common/io.c
index 937c710e06..cddb19c9a8 100644
--- a/uisimulator/common/io.c
+++ b/uisimulator/common/io.c
@@ -340,11 +340,12 @@ int sim_open(const char *name, int o, ...)
     if (num_openfiles >= MAX_OPEN_FILES)
         return -2;
 
-    if (o & O_CREAT)
+    if (opts & O_CREAT)
     {
         va_list ap;
         va_start(ap, o);
-        ret = OPEN(get_sim_pathname(name), opts, va_arg(ap, mode_t));
+        mode_t mode = va_arg(ap, unsigned int);
+        ret = OPEN(get_sim_pathname(name), opts, mode);
         va_end(ap);
     }
     else