diff --git a/autoconf/m4/huge_val.m4 b/autoconf/m4/huge_val.m4
index 7ef9dcae694..9dc76f22350 100644
--- a/autoconf/m4/huge_val.m4
+++ b/autoconf/m4/huge_val.m4
@@ -6,7 +6,7 @@ AC_DEFUN([AC_HUGE_VAL_CHECK],[
   AC_CACHE_CHECK([for HUGE_VAL sanity], [ac_cv_huge_val_sanity],[
     AC_LANG_PUSH([C++])
     ac_save_CXXFLAGS=$CXXFLAGS
-    CXXFLAGS+=" -pedantic"
+    CXXFLAGS="$CXXFLAGS -pedantic"
     AC_RUN_IFELSE(
       AC_LANG_PROGRAM(
         [#include <math.h>],
diff --git a/configure b/configure
index f4c5670de6e..5c2d466774d 100755
--- a/configure
+++ b/configure
@@ -16371,7 +16371,7 @@ ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ex
 ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
 
     ac_save_CXXFLAGS=$CXXFLAGS
-    CXXFLAGS+=" -pedantic"
+    CXXFLAGS="$CXXFLAGS -pedantic"
     if test "$cross_compiling" = yes; then
   ac_cv_huge_val_sanity=yes
 else