diff --git a/configure.ac b/configure.ac
index f4d5e4e..328d4bb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -21,10 +21,6 @@ AC_PROG_CC
 AC_PROG_CXX
 AC_PROG_LIBTOOL
 AX_C_LONG_LONG
-AX_CXX_HEADER_STDCXX_TR1
-if test "$ax_cv_cxx_stdcxx_tr1" != yes; then
-	AC_MSG_ERROR([Your version of gcc does not support the 'std::tr1' standard. Recommended gcc version is 4.1.2 or later. Please use a newer gcc version, or try to download the pre-compiled binaries from the fastx-toolkit website.])
-fi
 
 PKG_CHECK_MODULES([GTEXTUTILS],[gtextutils])
 
diff --git a/src/fastx_collapser/fastx_collapser.cpp b/src/fastx_collapser/fastx_collapser.cpp
index 6f90b01..aa79b58 100644
--- a/src/fastx_collapser/fastx_collapser.cpp
+++ b/src/fastx_collapser/fastx_collapser.cpp
@@ -47,8 +47,8 @@ const char* usage=
 "\n";
 
 FASTX fastx;
-#include <tr1/unordered_map>
-std::tr1::unordered_map<string,size_t> collapsed_sequences;
+#include <unordered_map>
+std::unordered_map<string,size_t> collapsed_sequences;
 std::list< pair<string,size_t> > sorted_collapsed_sequences ;
 
 struct PrintCollapsedSequence