diff --git a/headers/posix/limits.h b/headers/posix/limits.h
index d2699a1498..dfd707bb83 100644
--- a/headers/posix/limits.h
+++ b/headers/posix/limits.h
@@ -38,12 +38,11 @@
 #define NAME_MAX				(256)
 #define NGROUPS_MAX		 		(32)
 #define OPEN_MAX				(128)
-#define PAGE_SIZE				(4096)
 #define PAGESIZE				(4096)
 #define PATH_MAX				(1024)
 #define PIPE_MAX				(512)
 #define PTHREAD_KEYS_MAX		256
-#define PTHREAD_STACK_MIN		(2 * PAGE_SIZE)
+#define PTHREAD_STACK_MIN		(2 * PAGESIZE)
 #define SSIZE_MAX		  		__HAIKU_SADDR_MAX
 #define TTY_NAME_MAX			(256)
 #define TZNAME_MAX		  		(32)
@@ -76,6 +75,13 @@
 
 #define _POSIX2_LINE_MAX		(2048)
 
+/* The XSI name for PAGESIZE, with extra underscore included. Only define if
+ * _XOPEN_SOURCE was requested, otherwise it could conflict with the application.
+ */
+#ifdef _XOPEN_SOURCE
+#define PAGE_SIZE				PAGESIZE
+#endif
+
 /* _GCC_LIMITS_H_ is defined by GCC's internal limits.h to avoid
  * collisions with any defines in this file.
  */