diff --git a/cmake/Libraries.cmake b/cmake/Libraries.cmake
index c1eee27c7..e468a939c 100644
--- a/cmake/Libraries.cmake
+++ b/cmake/Libraries.cmake
@@ -89,7 +89,6 @@ macro(configure_unix_libs)
   include(CheckSymbolExists)
   include(CheckCSourceCompiles)
 
-  check_include_file_cxx(istream HAVE_ISTREAM)
   check_include_file_cxx(ostream HAVE_OSTREAM)
   check_include_file_cxx(sstream HAVE_SSTREAM)
 
diff --git a/src/lib/Config.h.in b/src/lib/Config.h.in
index 4b975ddc4..7bb52592a 100644
--- a/src/lib/Config.h.in
+++ b/src/lib/Config.h.in
@@ -19,9 +19,6 @@
 /* Define if you have the `inet_aton` function. */
 #cmakedefine HAVE_INET_ATON @HAVE_INET_ATON@
 
-/* Define to 1 if you have the <istream> header file. */
-#cmakedefine HAVE_ISTREAM @HAVE_ISTREAM@
-
 /* Define to 1 if you have the <locale.h> header file. */
 #cmakedefine HAVE_LOCALE_H @HAVE_LOCALE_H@