diff --git a/cmake/config-ix.cmake b/cmake/config-ix.cmake
index 28dee471ef0..3a2b91cc33c 100755
--- a/cmake/config-ix.cmake
+++ b/cmake/config-ix.cmake
@@ -4,6 +4,11 @@ include(CheckSymbolExists)
 include(CheckFunctionExists)
 include(CheckCXXSourceCompiles)
 
+if( UNIX )
+  # Used by check_symbol_exists:
+  set(CMAKE_REQUIRED_LIBRARIES m)
+endif()
+
 # Helper macros and functions
 macro(add_cxx_include result files)
   set(${result} "")
@@ -84,6 +89,7 @@ check_symbol_exists(isnan cmath HAVE_ISNAN_IN_CMATH)
 check_symbol_exists(isnan math.h HAVE_ISNAN_IN_MATH_H)
 check_symbol_exists(ceilf math.h HAVE_CEILF)
 check_symbol_exists(floorf math.h HAVE_FLOORF)
+check_symbol_exists(nearbyintf math.h HAVE_NEARBYINTF)
 check_symbol_exists(mallinfo malloc.h HAVE_MALLINFO)
 check_symbol_exists(malloc_zone_statistics malloc/malloc.h
                     HAVE_MALLOC_ZONE_STATISTICS)
diff --git a/include/llvm/Config/config.h.cmake b/include/llvm/Config/config.h.cmake
index fa8272798a4..2bec93f2469 100644
--- a/include/llvm/Config/config.h.cmake
+++ b/include/llvm/Config/config.h.cmake
@@ -253,7 +253,7 @@
 #cmakedefine HAVE_NDIR_H ${HAVE_NDIR_H}
 
 /* Define to 1 if you have the `nearbyintf' function. */
-#undef HAVE_NEARBYINTF
+#cmakedefine HAVE_NEARBYINTF ${HAVE_NEARBYINTF}
 
 /* Define if the neat program is available */
 #cmakedefine HAVE_NEATO ${HAVE_NEATO}