diff --git a/src/c/unixfsys.d b/src/c/unixfsys.d
index 058ef4edf..56a6e48ea 100644
--- a/src/c/unixfsys.d
+++ b/src/c/unixfsys.d
@@ -1193,7 +1193,9 @@ si_mkdir(cl_object directory, cl_object mode)
 #endif
   ecl_enable_interrupts();
 
-  if (ecl_unlikely(ok < 0)) {
+  if (ok < 0 && errno == EEXIST) {
+    @(return ECL_NIL);
+  } else if (ecl_unlikely(ok < 0)) {
     cl_object c_error = _ecl_strerror(errno);
     const char *msg = "Could not create directory ~S"
       "~%C library error: ~S";
diff --git a/src/cmp/proclamations.lsp b/src/cmp/proclamations.lsp
index 84bffce47..9e5eb594f 100644
--- a/src/cmp/proclamations.lsp
+++ b/src/cmp/proclamations.lsp
@@ -1114,7 +1114,7 @@
 (proclamation ext:mkstemp (pathname-designator) (or null pathname))
 (proclamation ext:copy-file (pathname-designator pathname-designator) gen-bool)
 
-(proclamation si:mkdir (pathname-designator unsigned-byte) string)
+(proclamation si:mkdir (pathname-designator unsigned-byte) (or string null))
 (proclamation si:rmdir (pathname-designator) null)
 
 
diff --git a/src/lsp/mislib.lsp b/src/lsp/mislib.lsp
index 3502f5809..1638655fe 100644
--- a/src/lsp/mislib.lsp
+++ b/src/lsp/mislib.lsp
@@ -292,12 +292,13 @@ where CREATED is true only if we succeeded on creating all directories."
       (dolist (item (pathname-directory full-pathname))
         (setf d (nconc d (list item)))
         (let* ((p (make-pathname :directory d :defaults *default-pathname-defaults*)))
-          (unless (or (symbolp item) (si::file-kind p nil))
-            (setf created t)
-            (let ((ps (namestring p)))
-              (when verbose
-                (format t "~%;;; Making directory ~A" ps))
-              (si::mkdir ps mode)))))
+          (unless (symbolp item)
+            (let* ((ps (namestring p))
+                   (newly-created (si::mkdir ps mode)))
+              (when newly-created
+                (setf created t)
+                (when verbose
+                  (format t "~%;;; Making directory ~A" ps)))))))
       (values pathname created))))
 
 (defmacro with-hash-table-iterator ((iterator package) &body body)