diff --git a/eo/configure.in b/eo/configure.in
index a728dd4f7..ed5513960 100644
--- a/eo/configure.in
+++ b/eo/configure.in
@@ -26,7 +26,7 @@ AC_CHECK_LIB(m, main)
 dnl Checks for header files.
 AC_HEADER_STDC
 AC_CHECK_HEADERS(limits.h)
-#AC_CXX_HAVE_SSTREAM
+AC_CXX_HAVE_SSTREAM
 
 dnl Checks for typedefs, structures, and compiler characteristics.
 AC_C_CONST