diff --git a/NEWS b/NEWS
index eedd6bc5914..adcfe8faa76 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,7 @@ PHP                                                                        NEWS
     (Nikita)
   . Fixed bug #78066 (PHP eats the first byte of a program that comes from
     process substitution). (Nikita)
+  . Fixed bug #52752 (Crash when lexing). (Nikita)
 
 - Libxml:
   . Fixed bug #78279 (libxml_disable_entity_loader settings is shared between
diff --git a/Zend/zend_stream.c b/Zend/zend_stream.c
index 4b32203cbb7..87ed617ef05 100644
--- a/Zend/zend_stream.c
+++ b/Zend/zend_stream.c
@@ -23,27 +23,6 @@
 #include "zend_compile.h"
 #include "zend_stream.h"
 
-#if HAVE_MMAP
-# if HAVE_UNISTD_H
-#  include <unistd.h>
-#  if defined(_SC_PAGESIZE)
-#    define REAL_PAGE_SIZE sysconf(_SC_PAGESIZE);
-#  elif defined(_SC_PAGE_SIZE)
-#    define REAL_PAGE_SIZE sysconf(_SC_PAGE_SIZE);
-#  endif
-# endif
-# if HAVE_SYS_MMAN_H
-#  include <sys/mman.h>
-# endif
-# ifndef REAL_PAGE_SIZE
-#  ifdef PAGE_SIZE
-#   define REAL_PAGE_SIZE PAGE_SIZE
-#  else
-#   define REAL_PAGE_SIZE 4096
-#  endif
-# endif
-#endif
-
 ZEND_DLIMPORT int isatty(int fd);
 
 static size_t zend_stream_stdio_reader(void *handle, char *buf, size_t len) /* {{{ */
@@ -73,17 +52,10 @@ static size_t zend_stream_stdio_fsizer(void *handle) /* {{{ */
 } /* }}} */
 
 static void zend_stream_unmap(zend_stream *stream) { /* {{{ */
-#if HAVE_MMAP
-	if (stream->mmap.map) {
-		munmap(stream->mmap.map, stream->mmap.len + ZEND_MMAP_AHEAD);
-	} else
-#endif
 	if (stream->mmap.buf) {
 		efree(stream->mmap.buf);
 	}
 	stream->mmap.len = 0;
-	stream->mmap.pos = 0;
-	stream->mmap.map = 0;
 	stream->mmap.buf = 0;
 	stream->handle   = stream->mmap.old_handle;
 } /* }}} */
@@ -197,7 +169,6 @@ ZEND_API int zend_stream_fixup(zend_file_handle *file_handle, char **buf, size_t
 			break;
 
 		case ZEND_HANDLE_MAPPED:
-			file_handle->handle.stream.mmap.pos = 0;
 			*buf = file_handle->handle.stream.mmap.buf;
 			*len = file_handle->handle.stream.mmap.len;
 			return SUCCESS;
@@ -215,30 +186,6 @@ ZEND_API int zend_stream_fixup(zend_file_handle *file_handle, char **buf, size_t
 	file_handle->type = ZEND_HANDLE_STREAM;  /* we might still be _FP but we need fsize() work */
 
 	if (old_type == ZEND_HANDLE_FP && !file_handle->handle.stream.isatty && size) {
-#if HAVE_MMAP
-		size_t page_size = REAL_PAGE_SIZE;
-
-		if (file_handle->handle.fp &&
-		    size != 0 &&
-		    ((size - 1) % page_size) <= page_size - ZEND_MMAP_AHEAD) {
-			/*  *buf[size] is zeroed automatically by the kernel */
-			*buf = mmap(0, size + ZEND_MMAP_AHEAD, PROT_READ, MAP_PRIVATE, fileno(file_handle->handle.fp), 0);
-			if (*buf != MAP_FAILED) {
-				zend_long offset = ftell(file_handle->handle.fp);
-				file_handle->handle.stream.mmap.map = *buf;
-
-				if (offset != -1) {
-					*buf += offset;
-					size -= offset;
-				}
-				file_handle->handle.stream.mmap.buf = *buf;
-				file_handle->handle.stream.mmap.len = size;
-
-				goto return_mapped;
-			}
-		}
-#endif
-		file_handle->handle.stream.mmap.map = 0;
 		file_handle->handle.stream.mmap.buf = *buf = safe_emalloc(1, size, ZEND_MMAP_AHEAD);
 		file_handle->handle.stream.mmap.len = zend_stream_read(file_handle, *buf, size);
 	} else {
@@ -255,7 +202,6 @@ ZEND_API int zend_stream_fixup(zend_file_handle *file_handle, char **buf, size_t
 				remain = size;
 			}
 		}
-		file_handle->handle.stream.mmap.map = 0;
 		file_handle->handle.stream.mmap.len = size;
 		if (size && remain < ZEND_MMAP_AHEAD) {
 			*buf = safe_erealloc(*buf, size, 1, ZEND_MMAP_AHEAD);
@@ -271,11 +217,7 @@ ZEND_API int zend_stream_fixup(zend_file_handle *file_handle, char **buf, size_t
 	if (ZEND_MMAP_AHEAD) {
 		memset(file_handle->handle.stream.mmap.buf + file_handle->handle.stream.mmap.len, 0, ZEND_MMAP_AHEAD);
 	}
-#if HAVE_MMAP
-return_mapped:
-#endif
 	file_handle->type = ZEND_HANDLE_MAPPED;
-	file_handle->handle.stream.mmap.pos        = 0;
 	file_handle->handle.stream.mmap.old_handle = file_handle->handle.stream.handle;
 	file_handle->handle.stream.mmap.old_closer = file_handle->handle.stream.closer;
 	file_handle->handle.stream.handle          = &file_handle->handle.stream;
diff --git a/Zend/zend_stream.h b/Zend/zend_stream.h
index c98969a3b4f..cf6d76437b3 100644
--- a/Zend/zend_stream.h
+++ b/Zend/zend_stream.h
@@ -44,8 +44,6 @@ typedef enum {
 
 typedef struct _zend_mmap {
 	size_t      len;
-	size_t      pos;
-	void        *map;
 	char        *buf;
 	void                  *old_handle;
 	zend_stream_closer_t   old_closer;
diff --git a/main/main.c b/main/main.c
index 66cf8df419d..c9d37ac2e00 100644
--- a/main/main.c
+++ b/main/main.c
@@ -84,27 +84,6 @@
 #include "rfc1867.h"
 
 #include "ext/standard/html_tables.h"
-
-#if HAVE_MMAP || defined(PHP_WIN32)
-# if HAVE_UNISTD_H
-#  include <unistd.h>
-#  if defined(_SC_PAGESIZE)
-#    define REAL_PAGE_SIZE sysconf(_SC_PAGESIZE);
-#  elif defined(_SC_PAGE_SIZE)
-#    define REAL_PAGE_SIZE sysconf(_SC_PAGE_SIZE);
-#  endif
-# endif
-# if HAVE_SYS_MMAN_H
-#  include <sys/mman.h>
-# endif
-# ifndef REAL_PAGE_SIZE
-#  ifdef PAGE_SIZE
-#   define REAL_PAGE_SIZE PAGE_SIZE
-#  else
-#   define REAL_PAGE_SIZE 4096
-#  endif
-# endif
-#endif
 /* }}} */
 
 PHPAPI int (*php_register_internal_extensions_func)(void) = php_register_internal_extensions;
@@ -1583,13 +1562,6 @@ static void php_zend_stream_closer(void *handle) /* {{{ */
 }
 /* }}} */
 
-static void php_zend_stream_mmap_closer(void *handle) /* {{{ */
-{
-	php_stream_mmap_unmap((php_stream*)handle);
-	php_zend_stream_closer(handle);
-}
-/* }}} */
-
 static size_t php_zend_stream_fsizer(void *handle) /* {{{ */
 {
 	php_stream_statbuf  ssb;
@@ -1608,38 +1580,18 @@ static int php_stream_open_for_zend(const char *filename, zend_file_handle *hand
 
 PHPAPI int php_stream_open_for_zend_ex(const char *filename, zend_file_handle *handle, int mode) /* {{{ */
 {
-	char *p;
-	size_t len, mapped_len;
 	php_stream *stream = php_stream_open_wrapper((char *)filename, "rb", mode, &handle->opened_path);
 
 	if (stream) {
-#if HAVE_MMAP || defined(PHP_WIN32)
-		size_t page_size = REAL_PAGE_SIZE;
-#endif
-
+		handle->type = ZEND_HANDLE_STREAM;
 		handle->filename = (char*)filename;
 		handle->free_filename = 0;
 		handle->handle.stream.handle  = stream;
 		handle->handle.stream.reader  = (zend_stream_reader_t)_php_stream_read;
 		handle->handle.stream.fsizer  = php_zend_stream_fsizer;
 		handle->handle.stream.isatty  = 0;
-		/* can we mmap immediately? */
 		memset(&handle->handle.stream.mmap, 0, sizeof(handle->handle.stream.mmap));
-		len = php_zend_stream_fsizer(stream);
-		if (len != 0
-#if HAVE_MMAP || defined(PHP_WIN32)
-		&& ((len - 1) % page_size) <= page_size - ZEND_MMAP_AHEAD
-#endif
-		&& php_stream_mmap_possible(stream)
-		&& (p = php_stream_mmap_range(stream, 0, len, PHP_STREAM_MAP_MODE_SHARED_READONLY, &mapped_len)) != NULL) {
-			handle->handle.stream.closer   = php_zend_stream_mmap_closer;
-			handle->handle.stream.mmap.buf = p;
-			handle->handle.stream.mmap.len = mapped_len;
-			handle->type = ZEND_HANDLE_MAPPED;
-		} else {
-			handle->handle.stream.closer = php_zend_stream_closer;
-			handle->type = ZEND_HANDLE_STREAM;
-		}
+		handle->handle.stream.closer = php_zend_stream_closer;
 		/* suppress warning if this stream is not explicitly closed */
 		php_stream_auto_cleanup(stream);