--- a/configure.ac
+++ b/configure.ac
@@ -18,7 +18,7 @@
 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
 
@@ -26,7 +26,7 @@
 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
 
--- a/sample/Makefile.am
+++ b/sample/Makefile.am
@@ -1,10 +1,10 @@
 #noinst_PROGRAMS = encode listcap names posix simple sql syntax crnl
 
-lib_onig = ../src/libonig.la
+lib_onig = $(top_builddir)/src/libonig.la
 LDADD  = $(lib_onig)
 
 AM_LDFLAGS  = -L$(prefix)/lib
-AM_CPPFLAGS = -I../src -I$(includedir)
+AM_CPPFLAGS = -I$(top_srcdir)/src
 
 TESTS = encode listcap names posix simple sql syntax user_property bug_fix
 
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -1,9 +1,9 @@
 ## Makefile.am for Oniguruma
-lib_onig = ../src/libonig.la
+lib_onig = $(top_builddir)/src/libonig.la
 
 AM_LDFLAGS  = -L$(prefix)/lib
 AM_CFLAGS =
-AM_CPPFLAGS = -I../src -I$(includedir)
+AM_CPPFLAGS = -I$(top_srcdir)/src
 
 TESTS = testc testp testcu