diff --git a/unix/uxsftp.c b/unix/uxsftp.c
index 0afd2a13..1c48e0d5 100644
--- a/unix/uxsftp.c
+++ b/unix/uxsftp.c
@@ -436,7 +436,10 @@ bool create_directory(const char *name)
 
 char *dir_file_cat(const char *dir, const char *file)
 {
-    return dupcat(dir, "/", file, NULL);
+    ptrlen dir_pl = ptrlen_from_asciz(dir);
+    return dupcat(
+        dir, ptrlen_endswith(dir_pl, PTRLEN_LITERAL("/"), NULL) ? "" : "/",
+        file, NULL);
 }
 
 /*
diff --git a/windows/winsftp.c b/windows/winsftp.c
index 45d38d57..adea38c8 100644
--- a/windows/winsftp.c
+++ b/windows/winsftp.c
@@ -451,7 +451,11 @@ bool create_directory(const char *name)
 
 char *dir_file_cat(const char *dir, const char *file)
 {
-    return dupcat(dir, "\\", file, NULL);
+    ptrlen dir_pl = ptrlen_from_asciz(dir);
+    return dupcat(
+        dir, (ptrlen_endswith(dir_pl, PTRLEN_LITERAL("\\"), NULL) ||
+              ptrlen_endswith(dir_pl, PTRLEN_LITERAL("/"), NULL)) ? "" : "\\",
+        file, NULL);
 }
 
 /* ----------------------------------------------------------------------