diff --git a/Makefile.am b/Makefile.am
index 2865fb7..75cbd45 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -6,7 +6,7 @@ libname = libonig.la
 ACLOCAL_AMFLAGS = -I m4
 #AM_CFLAGS = -DNOT_RUBY
 AM_CFLAGS =
-INCLUDES  = -I$(top_srcdir) -I$(includedir)
+INCLUDES  = -I$(top_srcdir)
 
 SUBDIRS = . sample
 
diff --git a/configure.in b/configure.in
index 1e21f96..51b56d8 100644
--- a/configure.in
+++ b/configure.in
@@ -25,7 +25,7 @@ dnl check for COMBINATION_EXPLOSION
 AC_ARG_ENABLE(combination-explosion-check,
 	[  --enable-combination-explosion-check   enable combination explosion check],
 	[comb_expl_check=$enableval])
-if test "${comb_expl_check}" = yes; then
+if test "x${comb_expl_check}" = xyes; then
   AC_DEFINE(USE_COMBINATION_EXPLOSION_CHECK,1,[Define if combination explosion check])
 fi
 
@@ -33,7 +33,7 @@ dnl check for CRNL_AS_LINE_TERMINATOR
 AC_ARG_ENABLE(crnl-as-line-terminator,
 	[  --enable-crnl-as-line-terminator   enable CR+NL as line terminator],
 	[crnl_as_line_terminator=$enableval])
-if test "${crnl_as_line_terminator}" = yes; then
+if test "x${crnl_as_line_terminator}" = xyes; then
   AC_DEFINE(USE_CRNL_AS_LINE_TERMINATOR,1,[Define if enable CR+NL as line terminator])
 fi
 
diff --git a/sample/Makefile.am b/sample/Makefile.am
index af33057..347af94 100644
--- a/sample/Makefile.am
+++ b/sample/Makefile.am
@@ -2,7 +2,7 @@ noinst_PROGRAMS = encode listcap names posix simple sql syntax crnl
 
 libname = $(top_builddir)/libonig.la
 LDADD   = $(libname)
-INCLUDES  = -I$(top_srcdir) -I$(includedir)
+INCLUDES  = -I$(top_srcdir)
 
 encode_SOURCES  = encode.c
 listcap_SOURCES = listcap.c