diff --git a/src/drivers/X11/Fl_X11_System_Driver.cxx b/src/drivers/X11/Fl_X11_System_Driver.cxx
index 88fa416f5..801189b44 100644
--- a/src/drivers/X11/Fl_X11_System_Driver.cxx
+++ b/src/drivers/X11/Fl_X11_System_Driver.cxx
@@ -481,8 +481,8 @@ int Fl_X11_System_Driver::filename_list(const char *d,
   fl_utf8to_mb(d, dirlen, dirloc, dirlen + 1);
 
 #ifndef HAVE_SCANDIR
-  // This version is when we define our own scandir
-  int n = fl_scandir(dirloc, list, 0, sort);
+  // This version is when we define our own scandir. Note it updates errmsg on errors.
+  int n = fl_scandir(dirloc, list, 0, sort, errmsg, errmsg_sz);
 #elif defined(HAVE_SCANDIR_POSIX)
   // POSIX (2008) defines the comparison function like this:
   int n = scandir(dirloc, list, 0, (int(*)(const dirent **, const dirent **))sort);
@@ -504,7 +504,11 @@ int Fl_X11_System_Driver::filename_list(const char *d,
   free(dirloc);
 
   if (n==-1) {
+    // Don't write to errmsg if FLTK's fl_scandir() already set it.
+    // If OS's scandir() was used (HAVE_SCANDIR), we return its error in errmsg here..
+#ifdef HAVE_SCANDIR
     if (errmsg) fl_snprintf(errmsg, errmsg_sz, "%s", strerror(errno));
+#endif
     return -1;
   }
 
diff --git a/src/scandir_posix.c b/src/scandir_posix.c
index 9d8396619..e83a12009 100644
--- a/src/scandir_posix.c
+++ b/src/scandir_posix.c
@@ -48,6 +48,7 @@
 #include <stddef.h>           /* For 'offsetof()', 'NULL' and 'size_t' */
 #include <limits.h>           /* For 'INT_MAX' */
 #include <string.h>           /* For 'memcpy()' */
+#include "flstring.h"         /* For 'fl_snprintf()' */
 #if defined(HAVE_PTHREAD) && defined(HAVE_PTHREAD_H)
 #  include <pthread.h>
 #endif  /* HAVE_PTHREAD */
@@ -137,7 +138,7 @@ int
 fl_scandir(const char *dir, struct dirent ***namelist,
            int (*sel)(struct dirent *),
            int (*compar)(struct dirent **, struct dirent **),
-           char *errmsg, int errmsg_sz) {
+           char *errmsg, int errmsg_sz)
 {
   int result = -1;
   DIR *dirp;