diff --git a/src/include/lam_config_bottom.h b/src/include/lam_config_bottom.h
index ac4903d83f..a66953fcaf 100644
--- a/src/include/lam_config_bottom.h
+++ b/src/include/lam_config_bottom.h
@@ -11,6 +11,7 @@
  */
 
 /* If we're in C, bring in the bool type and true/false constants. */
+#include <limits.h>
 
 #ifndef __cplusplus
 #ifdef HAVE_STDBOOL_H
@@ -19,3 +20,14 @@
 typedef enum { false, true } bool;
 #endif
 #endif
+
+/*
+ * Maximum size of a filename path.
+ */
+#if defined(PATH_MAX)
+#define LAM_PATH_MAX	(PATH_MAX + 1)
+#elif defined(_POSIX_PATH_MAX)
+#define LAM_PATH_MAX	(_POSIX_PATH_MAX + 1)
+#else
+#define LAM_PATH_MAX	256
+#endif