diff --git a/client/client_types.cpp b/client/client_types.cpp
index afe9aa9d1..3384506fb 100644
--- a/client/client_types.cpp
+++ b/client/client_types.cpp
@@ -22,15 +22,6 @@
 #include "zlib.h"
 #else
 #include "config.h"
-// Somehow having config.h define _FILE_OFFSET_BITS or _LARGE_FILES is
-// causing open to be redefined to open64 which somehow, in some versions
-// of zlib.h causes gzopen to be redefined as gzopen64 which subsequently gets
-// reported as a linker error.  So for this file, we compile in small files
-// mode, regardless of these settings
-#undef _FILE_OFFSET_BITS
-#undef _LARGE_FILES
-#undef _LARGEFILE_SOURCE
-#undef _LARGEFILE64_SOURCE
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <zlib.h>
diff --git a/client/hostinfo_unix.cpp b/client/hostinfo_unix.cpp
index cec9401f5..a5a4e3dcb 100644
--- a/client/hostinfo_unix.cpp
+++ b/client/hostinfo_unix.cpp
@@ -26,15 +26,6 @@
 
 #if !defined(_WIN32) || defined(__CYGWIN32__)
 
-// Access to binary files in /proc filesystem doesn't work in the 64bit
-// files environment on some systems.
-// None of the functions here need 64bit file functions,
-// so undefine _FILE_OFFSET_BITS and _LARGE_FILES.
-//
-#undef _FILE_OFFSET_BITS
-#undef _LARGE_FILES
-#undef _LARGEFILE_SOURCE
-#undef _LARGEFILE64_SOURCE
 #include <iostream>
 #include <vector>
 #include <string>
diff --git a/lib/mem_usage.cpp b/lib/mem_usage.cpp
index 8c1b9bf1a..9adbc7d5c 100644
--- a/lib/mem_usage.cpp
+++ b/lib/mem_usage.cpp
@@ -19,15 +19,6 @@
 #include "boinc_win.h"
 #else
 #include "config.h"
-#if HAVE_PROCFS_H
-// Can't use large file calls with solaris procfs.
-#if defined(_FILE_OFFSET_BITS) && ( _FILE_OFFSET_BITS == 64 )
-#undef _FILE_OFFSET_BITS
-#undef _LARGE_FILES
-#undef _LARGEFILE_SOURCE
-#undef _LARGEFILE64_SOURCE
-#endif
-#endif
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
diff --git a/lib/procinfo_unix.cpp b/lib/procinfo_unix.cpp
index 150906261..48ca7cd75 100644
--- a/lib/procinfo_unix.cpp
+++ b/lib/procinfo_unix.cpp
@@ -20,16 +20,6 @@
 
 #include "config.h"
 
-#if HAVE_PROCFS_H
-// Can't use large file calls with solaris procfs.
-#if defined(_FILE_OFFSET_BITS) && ( _FILE_OFFSET_BITS == 64 )
-#undef _FILE_OFFSET_BITS
-#undef _LARGE_FILES
-#undef _LARGEFILE_SOURCE
-#undef _LARGEFILE64_SOURCE
-#endif
-#endif
-
 #include <cstdio>
 #include <string.h>
 #include <sys/param.h>
diff --git a/samples/gfx_html/mongoose.cpp b/samples/gfx_html/mongoose.cpp
index 85d9fd638..c4f1c9053 100644
--- a/samples/gfx_html/mongoose.cpp
+++ b/samples/gfx_html/mongoose.cpp
@@ -52,7 +52,6 @@
 #ifndef _LARGEFILE_SOURCE
 #define _LARGEFILE_SOURCE       // Enable fseeko() and ftello() functions
 #endif
-#define _FILE_OFFSET_BITS 64    // Enable 64-bit file offsets
 
 #ifdef _MSC_VER
 #pragma warning (disable : 4127)  // FD_SET() emits warning, disable it