diff --git a/configure.ac b/configure.ac
index 703d267836..f4a6caf5dd 100644
--- a/configure.ac
+++ b/configure.ac
@@ -123,10 +123,6 @@ AC_SUBST([HAVE_WCHAR_T])
 
 # Needed for Mingw-w64
 AC_TYPE_LONG_LONG_INT
-if test "$ac_cv_type_long_long_int" = yes; then
-  AC_CHECK_SIZEOF(long)
-  AC_CHECK_SIZEOF(long long)
-fi
 
 ### We need iconv for unicode support (Qt4 frontend requires it too)
 LYX_USE_INCLUDED_ICONV
@@ -309,12 +305,6 @@ char * strerror(int n);
 #  define USE_WCHAR_T
 #endif
 
-#ifdef HAVE_LONG_LONG_INT
-#if SIZEOF_LONG_LONG > SIZEOF_LONG
-#define LYX_USE_LONG_LONG
-#endif
-#endif
-
 #endif
 ])
 
diff --git a/src/support/convert.cpp b/src/support/convert.cpp
index b1c554e083..9455643a66 100644
--- a/src/support/convert.cpp
+++ b/src/support/convert.cpp
@@ -105,7 +105,7 @@ docstring convert<docstring>(unsigned long ul)
 }
 
 
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 template<>
 string convert<string>(unsigned long long ull)
 {
@@ -135,7 +135,7 @@ docstring convert<docstring>(long l)
 }
 
 
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 template<>
 string convert<string>(long long ll)
 {
diff --git a/src/support/convert.h b/src/support/convert.h
index fb069c98c3..3b97fb6c88 100644
--- a/src/support/convert.h
+++ b/src/support/convert.h
@@ -33,13 +33,13 @@ template<> std::string convert<std::string>(unsigned int ui);
 template<> docstring convert<docstring>(unsigned int ui);
 template<> std::string convert<std::string>(unsigned long ul);
 template<> docstring convert<docstring>(unsigned long ul);
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 template<> std::string convert<std::string>(unsigned long long ull);
 template<> docstring convert<docstring>(unsigned long long ull);
 #endif
 template<> std::string convert<std::string>(long l);
 template<> docstring convert<docstring>(long l);
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 template<> std::string convert<std::string>(long long ll);
 template<> docstring convert<docstring>(long long ll);
 #endif
diff --git a/src/support/debug.cpp b/src/support/debug.cpp
index 3026df09f2..e72a43dbd1 100644
--- a/src/support/debug.cpp
+++ b/src/support/debug.cpp
@@ -240,7 +240,7 @@ LyXErr & operator<<(LyXErr & l, long t)
 { return toStream(l, t); }
 LyXErr & operator<<(LyXErr & l, unsigned long t)
 { return toStream(l, t); }
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 LyXErr & operator<<(LyXErr & l, long long t)
 { return toStream(l, t); }
 LyXErr & operator<<(LyXErr & l, unsigned long long t)
diff --git a/src/support/debug.h b/src/support/debug.h
index f6b06d5c3e..212049a609 100644
--- a/src/support/debug.h
+++ b/src/support/debug.h
@@ -202,7 +202,7 @@ LyXErr & operator<<(LyXErr &, int);
 LyXErr & operator<<(LyXErr &, unsigned int);
 LyXErr & operator<<(LyXErr &, long);
 LyXErr & operator<<(LyXErr &, unsigned long);
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 LyXErr & operator<<(LyXErr &, long long);
 LyXErr & operator<<(LyXErr &, unsigned long long);
 #endif
diff --git a/src/support/docstring.cpp b/src/support/docstring.cpp
index 496d4c0242..c53222da6d 100644
--- a/src/support/docstring.cpp
+++ b/src/support/docstring.cpp
@@ -514,7 +514,7 @@ protected:
 		return do_put_helper(oit, b, fill, v);
 	}
 
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 	iter_type
 	do_put(iter_type oit, ios_base & b, char_type fill, long long v) const
 	{
@@ -675,7 +675,7 @@ protected:
 		return do_get_integer(iit, eit, b, err, v);
 	}
 
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 	iter_type
 	do_get(iter_type iit, iter_type eit, ios_base & b,
 		ios_base::iostate & err, long long & v) const
diff --git a/src/support/lstrings.cpp b/src/support/lstrings.cpp
index e69fc8837b..3195762a4a 100644
--- a/src/support/lstrings.cpp
+++ b/src/support/lstrings.cpp
@@ -1475,7 +1475,7 @@ docstring bformat(docstring const & fmt, long arg1)
 }
 
 
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 docstring bformat(docstring const & fmt, long long arg1)
 {
 	LATTEST(contains(fmt, from_ascii("%1$d")));
diff --git a/src/support/lstrings.h b/src/support/lstrings.h
index fcf1cbb6fe..1ff9dfd811 100644
--- a/src/support/lstrings.h
+++ b/src/support/lstrings.h
@@ -360,7 +360,7 @@ docstring to_percent_encoding(docstring const & in, docstring const & ex = docst
 
 docstring bformat(docstring const & fmt, int arg1);
 docstring bformat(docstring const & fmt, long arg1);
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 docstring bformat(docstring const & fmt, long long arg1);
 #endif
 docstring bformat(docstring const & fmt, unsigned int arg1);
diff --git a/src/texstream.cpp b/src/texstream.cpp
index f8f298bdaf..1523ca9470 100644
--- a/src/texstream.cpp
+++ b/src/texstream.cpp
@@ -330,7 +330,7 @@ template otexrowstream & operator<< <unsigned int>(otexrowstream &,
 template otexrowstream & operator<< <unsigned long>(otexrowstream &,
 													unsigned long);
 
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 template otexrowstream & operator<< <unsigned long long>(otexrowstream &,
                                                          unsigned long long);
 #endif
@@ -351,7 +351,7 @@ template otexstream & operator<< <double>(otexstream &, double);
 template otexstream & operator<< <int>(otexstream &, int);
 template otexstream & operator<< <unsigned int>(otexstream &, unsigned int);
 template otexstream & operator<< <unsigned long>(otexstream &, unsigned long);
-#ifdef LYX_USE_LONG_LONG
+#ifdef HAVE_LONG_LONG_INT
 template otexstream & operator<< <unsigned long long>(otexstream &, unsigned long long);
 #endif