diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc
index eaf695b81..582238d15 100644
--- a/winsup/cygwin/path.cc
+++ b/winsup/cygwin/path.cc
@@ -5120,7 +5120,7 @@ dirname (char *path)
     return strcpy (buf, ".");
   if (isalpha (path[0]) && path[1] == ':')
     bs += 2;
-  else if (strspn (path, "/\\") > 1)
+  else if (strspn (path, "/\\") == 2)
     ++bs;
   c = strrchr (bs, '/');
   if ((d = strrchr (c ?: bs, '\\')) > c)
diff --git a/winsup/cygwin/release/3.4.7 b/winsup/cygwin/release/3.4.7
index a121d81b6..2c305ec5f 100644
--- a/winsup/cygwin/release/3.4.7
+++ b/winsup/cygwin/release/3.4.7
@@ -6,3 +6,6 @@ Bug Fixes
 
 - kill(1): don't print spurious error message.
   Addresses: https://cygwin.com/pipermail/cygwin/2023-March/253291.html
+
+- Align behaviour of dirname in terms of leading slashes to POSIX:
+  https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html