diff --git a/config/configure b/config/configure
index b36f2f065..9f0b1869a 100755
--- a/config/configure
+++ b/config/configure
@@ -1452,13 +1452,10 @@ buildinc=$ctroot/build/include
 buildlib=$ctroot/build/lib/$target
 
 
-if test -n "${OS_IS_DARWIN}"; then
-cat >>confdefs.h <<\_ACEOF
-#define DARWIN 1
+cat >>confdefs.h <<_ACEOF
+#define DARWIN $OS_IS_DARWIN
 _ACEOF
 
-fi
-
 cat >>confdefs.h <<_ACEOF
 #define RXNPATH_FONT "$RPFONT"
 _ACEOF
@@ -3159,7 +3156,7 @@ fi
 
 
 # Provide some information about the compiler.
-echo "$as_me:3162:" \
+echo "$as_me:3159:" \
      "checking for Fortran 77 compiler version" >&5
 ac_compiler=`set X $ac_compile; echo $2`
 { (eval echo "$as_me:$LINENO: \"$ac_compiler --version </dev/null >&5\"") >&5
@@ -3336,7 +3333,7 @@ _ACEOF
 # flags.
 ac_save_FFLAGS=$FFLAGS
 FFLAGS="$FFLAGS $ac_verb"
-(eval echo $as_me:3339: \"$ac_link\") >&5
+(eval echo $as_me:3336: \"$ac_link\") >&5
 ac_f77_v_output=`eval $ac_link 5>&1 2>&1 | grep -v 'Driving:'`
 echo "$ac_f77_v_output" >&5
 FFLAGS=$ac_save_FFLAGS
@@ -3416,7 +3413,7 @@ _ACEOF
 # flags.
 ac_save_FFLAGS=$FFLAGS
 FFLAGS="$FFLAGS $ac_cv_prog_f77_v"
-(eval echo $as_me:3419: \"$ac_link\") >&5
+(eval echo $as_me:3416: \"$ac_link\") >&5
 ac_f77_v_output=`eval $ac_link 5>&1 2>&1 | grep -v 'Driving:'`
 echo "$ac_f77_v_output" >&5
 FFLAGS=$ac_save_FFLAGS
diff --git a/config/configure.in b/config/configure.in
index 900282073..4f26a68c6 100755
--- a/config/configure.in
+++ b/config/configure.in
@@ -127,10 +127,7 @@ AC_SUBST(buildinc)
 buildlib=$ctroot/build/lib/$target
 AC_SUBST(buildlib)
 
-if test -n "${OS_IS_DARWIN}"; then 
-AC_DEFINE(DARWIN)
-fi
-
+AC_DEFINE_UNQUOTED(DARWIN,$OS_IS_DARWIN)
 AC_DEFINE_UNQUOTED(RXNPATH_FONT,"$RPFONT")
 AC_DEFINE_UNQUOTED(CANTERA_ROOT,"$prefix/cantera")