diff --git a/configure.in b/configure.in
index 6aa8fed..c845644 100644
--- a/configure.in
+++ b/configure.in
@@ -86,7 +86,7 @@ dnl --------------------------------------------------------------
 dnl Checks for header files.
 dnl --------------------------------------------------------------
 AC_HEADER_STDC
-AC_CHECK_HEADERS(fcntl.h unistd.h sys/wait.h sys/stats.h sys/types.h)
+AC_CHECK_HEADERS(fcntl.h unistd.h sys/stats.h sys/types.h)
 AC_CHECK_HEADERS(arpa/inet.h netinet/in.h)
 AC_CHECK_HEADERS([readline/readline.h], [has_readline=1], [has_readline=0])
 AM_CONDITIONAL(HAS_READLINE, test "$has_readline" = "1")
diff --git a/dic/automaton.cpp b/dic/automaton.cpp
index cba5c75..6373597 100644
--- a/dic/automaton.cpp
+++ b/dic/automaton.cpp
@@ -26,10 +26,6 @@
 #include <sstream>
 #include <cstring>
 #include <cstdio>
-#include <sys/types.h>
-#ifdef HAVE_SYS_WAIT_H
-#   include <sys/wait.h>
-#endif
 
 #include "dic.h"
 #include "regexp.h"
@@ -244,20 +240,6 @@ void Automaton::dump(const string &iFileName) const
     fprintf(f, "fontsize=20;\n");
     fprintf(f, "}\n");
     fclose(f);
-
-#ifdef HAVE_SYS_WAIT_H
-    pid_t pid = fork ();
-    if (pid > 0)
-    {
-        wait(NULL);
-    }
-    else if (pid == 0)
-    {
-        execlp("dotty", "dotty", iFileName.c_str(), NULL);
-        printf("exec dotty failed\n");
-        exit(1);
-    }
-#endif
 }
 
 
@@ -560,20 +542,6 @@ void AutomatonHelper::dump(const string &iFileName) const
     fprintf(f, "fontsize=20;\n");
     fprintf(f, "}\n");
     fclose(f);
-
-#ifdef HAVE_SYS_WAIT_H
-    pid_t pid = fork();
-    if (pid > 0)
-    {
-        wait(NULL);
-    }
-    else if (pid == 0)
-    {
-        execlp("dotty", "dotty", iFileName.c_str(), NULL);
-        printf("exec dotty failed\n");
-        exit(1);
-    }
-#endif
 }
 #endif
 
diff --git a/dic/regexp.cpp b/dic/regexp.cpp
index a7ebdca..17a741f 100644
--- a/dic/regexp.cpp
+++ b/dic/regexp.cpp
@@ -25,9 +25,6 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
-#ifdef HAVE_SYS_WAIT_H
-#   include <sys/wait.h>
-#endif
 #include <unistd.h>
 
 #include "dic.h"
@@ -264,20 +261,6 @@ void Node::printTreeDot(const string &iFileName, int detail) const
     fprintf(f, "fontsize=20;\n");
     fprintf(f, "}\n");
     fclose(f);
-
-#ifdef HAVE_SYS_WAIT_H
-    pid_t pid = fork();
-    if (pid > 0)
-    {
-        wait(NULL);
-    }
-    else if (pid == 0)
-    {
-        execlp("dotty", "dotty", iFileName.c_str(), NULL);
-        printf("exec dotty failed\n");
-        exit(1);
-    }
-#endif
 }
 #endif