diff --git a/Error-log b/Error-log
index e38de8b..34d020e 100644
--- a/Error-log
+++ b/Error-log
@@ -107,3 +107,5 @@ October 1996.
 
 transcendental functions broken (sin, cos, tan, log)
 reported by jsc 8 Nov 96. Fixed by ???????????
+
+Fixed up initial sizes for allocated filename buffers to be _POSIX_PATH_MAX.
diff --git a/scsh/syscalls1.c b/scsh/syscalls1.c
index c171bef..f4550ee 100644
--- a/scsh/syscalls1.c
+++ b/scsh/syscalls1.c
@@ -176,11 +176,20 @@ int set_cloexec(int fd, int val)
 *******************************************************************************
 */
 
+/* Posix rules: If PATH_MAX is defined, it's the length of longest path.
+** Otherwise, _POSIX_PATH_MAX = 255, and is a lower bound on said length.
+*/
+#ifdef PATH_MAX
+#define scsh_path_max (PATH_MAX)
+#else
+#define scsh_path_max (_POSIX_PATH_MAX)
+#endif
+
 /* Simple-minded POSIX version. */
 int scheme_cwd(const char **dirp)
 {
   char *buf;
-  int size = 100;
+  int size = scsh_path_max + 1; /* +1 for terminating nul byte... */
 
   buf = Malloc(char,size);
   if(!buf) goto lose;