diff --git a/.cspell/words.txt b/.cspell/words.txt
index f93a3b0..fc328e9 100644
--- a/.cspell/words.txt
+++ b/.cspell/words.txt
@@ -1,6 +1,9 @@
 bdiff
 cmake_current_source_dir
+dhave_unistd_h
+dhave_unistd_h
 fpatch
+have_unistd_h
 intdiff
 intdifftest
 kubo
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7b08f20..42739e3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,11 +6,18 @@ project(
   VERSION 1.21
 )
 
+include(CheckIncludeFile)
+
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
+check_include_file(unistd.h HAVE_UNISTD_H)
+if(HAVE_UNISTD_H)
+  add_definitions(-DHAVE_UNISTD_H)
+endif()
+
 include_directories(BEFORE ${CMAKE_CURRENT_SOURCE_DIR}/include)
 
 option(DTL_ENABLE_TESTING "Enable DTL unit tests" OFF)
diff --git a/examples/common.hpp b/examples/common.hpp
index 6d699b0..734ba76 100644
--- a/examples/common.hpp
+++ b/examples/common.hpp
@@ -1,6 +1,19 @@
 #ifndef DTL_EXAMPLE_COMMON_H
 #define DTL_EXAMPLE_COMMON_H
 
+#include <cassert>
+#include <cstdio>
+#include <fstream>
+#include <sstream>
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <time.h>
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif // HAVE_UNISTD_H
+
 #include "dtl/dtl.hpp"
 
 bool isFileExist(std::string &fs);
diff --git a/include/dtl/Lcs.hpp b/include/dtl/Lcs.hpp
index 1b85ca4..4b4a4c5 100644
--- a/include/dtl/Lcs.hpp
+++ b/include/dtl/Lcs.hpp
@@ -38,7 +38,6 @@
 #ifndef DTL_LCS_H
 #define DTL_LCS_H
 
-#include "dtl/variables.hpp"
 #include "dtl/Sequence.hpp"
 
 namespace dtl {
diff --git a/include/dtl/Sequence.hpp b/include/dtl/Sequence.hpp
index 1a34ce9..ad25b69 100644
--- a/include/dtl/Sequence.hpp
+++ b/include/dtl/Sequence.hpp
@@ -38,8 +38,9 @@
 #ifndef DTL_SEQUENCE_H
 #define DTL_SEQUENCE_H
 
-namespace dtl {
+#include <vector>
 
+namespace dtl {
 /**
  * sequence class template
  */
diff --git a/include/dtl/Ses.hpp b/include/dtl/Ses.hpp
index ce68095..ca44762 100644
--- a/include/dtl/Ses.hpp
+++ b/include/dtl/Ses.hpp
@@ -38,6 +38,9 @@
 #ifndef DTL_SES_H
 #define DTL_SES_H
 
+#include <utility>
+#include <vector>
+
 #include "dtl/variables.hpp"
 #include "dtl/Sequence.hpp"
 
@@ -48,7 +51,7 @@ namespace dtl {
  */
 template <typename elem> class Ses : public Sequence<elem> {
 private:
-  typedef pair<elem, elemInfo> sesElem;
+  typedef std::pair<elem, elemInfo> sesElem;
   typedef std::vector<sesElem> sesElemVec;
 
 public:
diff --git a/include/dtl/dtl.hpp b/include/dtl/dtl.hpp
index 6d2bff1..1f0a691 100644
--- a/include/dtl/dtl.hpp
+++ b/include/dtl/dtl.hpp
@@ -36,24 +36,6 @@
 #ifndef DTL_H
 #define DTL_H
 
-#include <algorithm>
-#include <cassert>
-#include <cstdio>
-#include <fstream>
-#include <iostream>
-#include <list>
-#include <sstream>
-#include <string>
-#include <vector>
-
-#include <fcntl.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <time.h>
-#ifdef HAVE_UNISTD_H
-#include <unistd.h>
-#endif // HAVE_UNISTD_H
-
 #include "dtl/Diff.hpp"
 #include "dtl/Diff3.hpp"
 #include "dtl/Lcs.hpp"
diff --git a/include/dtl/functors.hpp b/include/dtl/functors.hpp
index d25a343..5cd1709 100644
--- a/include/dtl/functors.hpp
+++ b/include/dtl/functors.hpp
@@ -38,6 +38,8 @@
 #ifndef DTL_FUNCTORS_H
 #define DTL_FUNCTORS_H
 
+#include <iostream>
+
 #include "dtl/variables.hpp"
 
 namespace dtl {
diff --git a/include/dtl/variables.hpp b/include/dtl/variables.hpp
index 2f69803..e93f843 100644
--- a/include/dtl/variables.hpp
+++ b/include/dtl/variables.hpp
@@ -38,6 +38,12 @@
 #ifndef DTL_VARIABLES_H
 #define DTL_VARIABLES_H
 
+#include <algorithm>
+#include <iostream>
+#include <list>
+#include <string>
+#include <vector>
+
 namespace dtl {
 
 using std::cout;
diff --git a/test/dtl_test_common.hpp b/test/dtl_test_common.hpp
index d0a75d4..023a7cd 100644
--- a/test/dtl_test_common.hpp
+++ b/test/dtl_test_common.hpp
@@ -1,6 +1,9 @@
 #ifndef DTL_TEST_COMMON
 #define DTL_TEST_COMMON
 
+#include <cstdio>
+#include <fstream>
+
 #include <gtest/gtest.h>
 
 #include "dtl/dtl.hpp"