diff --git a/biconcor/Alignment.cpp b/biconcor/Alignment.cpp
index 814802531..a18775c1f 100644
--- a/biconcor/Alignment.cpp
+++ b/biconcor/Alignment.cpp
@@ -2,7 +2,7 @@
 
 #include <fstream>
 #include <string>
-#include <stdlib.h>
+#include <cstdlib>
 #include <cstring>
 
 namespace
diff --git a/biconcor/Mismatch.cpp b/biconcor/Mismatch.cpp
index c3afec781..8e029bf19 100644
--- a/biconcor/Mismatch.cpp
+++ b/biconcor/Mismatch.cpp
@@ -4,7 +4,7 @@
 #include <iostream>
 #include <cstring>
 #include <string>
-#include <stdlib.h>
+#include <cstdlib>
 
 #include "SuffixArray.h"
 #include "TargetCorpus.h"
diff --git a/biconcor/PhrasePairCollection.cpp b/biconcor/PhrasePairCollection.cpp
index dd21faad3..540aaac6f 100644
--- a/biconcor/PhrasePairCollection.cpp
+++ b/biconcor/PhrasePairCollection.cpp
@@ -1,6 +1,6 @@
 #include "PhrasePairCollection.h"
 
-#include <stdlib.h>
+#include <cstdlib>
 #include <cstring>
 #include <algorithm>
 
diff --git a/biconcor/SuffixArray.cpp b/biconcor/SuffixArray.cpp
index f4122a2d8..9566ede99 100644
--- a/biconcor/SuffixArray.cpp
+++ b/biconcor/SuffixArray.cpp
@@ -2,7 +2,7 @@
 
 #include <fstream>
 #include <string>
-#include <stdlib.h>
+#include <cstdlib>
 #include <cstring>
 
 namespace
diff --git a/biconcor/TargetCorpus.cpp b/biconcor/TargetCorpus.cpp
index 06468007f..da35801c8 100644
--- a/biconcor/TargetCorpus.cpp
+++ b/biconcor/TargetCorpus.cpp
@@ -2,7 +2,7 @@
 
 #include <fstream>
 #include <string>
-#include <stdlib.h>
+#include <cstdlib>
 #include <cstring>
 
 namespace