diff --git a/src/crypto/flex/cryptonote/cryptonight_dark.c b/src/crypto/flex/cryptonote/cryptonight_dark.c
index 32b01968..d96da1fc 100644
--- a/src/crypto/flex/cryptonote/cryptonight_dark.c
+++ b/src/crypto/flex/cryptonote/cryptonight_dark.c
@@ -6,6 +6,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include "crypto/oaes_lib.h"
 #include "crypto/c_keccak.h"
 #include "crypto/c_groestl.h"
diff --git a/src/crypto/flex/cryptonote/cryptonight_dark_lite.c b/src/crypto/flex/cryptonote/cryptonight_dark_lite.c
index d2f482de..9ff329d5 100644
--- a/src/crypto/flex/cryptonote/cryptonight_dark_lite.c
+++ b/src/crypto/flex/cryptonote/cryptonight_dark_lite.c
@@ -6,6 +6,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include "crypto/oaes_lib.h"
 #include "crypto/c_keccak.h"
 #include "crypto/c_groestl.h"
diff --git a/src/crypto/flex/cryptonote/cryptonight_fast.c b/src/crypto/flex/cryptonote/cryptonight_fast.c
index 46f26aff..41df800b 100644
--- a/src/crypto/flex/cryptonote/cryptonight_fast.c
+++ b/src/crypto/flex/cryptonote/cryptonight_fast.c
@@ -6,6 +6,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include "crypto/oaes_lib.h"
 #include "crypto/c_keccak.h"
 #include "crypto/c_groestl.h"
diff --git a/src/crypto/flex/cryptonote/cryptonight_lite.c b/src/crypto/flex/cryptonote/cryptonight_lite.c
index d9be39cd..6b060690 100644
--- a/src/crypto/flex/cryptonote/cryptonight_lite.c
+++ b/src/crypto/flex/cryptonote/cryptonight_lite.c
@@ -6,6 +6,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include "crypto/oaes_lib.h"
 #include "crypto/c_keccak.h"
 #include "crypto/c_groestl.h"
diff --git a/src/crypto/flex/cryptonote/cryptonight_turtle.c b/src/crypto/flex/cryptonote/cryptonight_turtle.c
index 57163073..aa4cd850 100644
--- a/src/crypto/flex/cryptonote/cryptonight_turtle.c
+++ b/src/crypto/flex/cryptonote/cryptonight_turtle.c
@@ -6,6 +6,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include "crypto/oaes_lib.h"
 #include "crypto/c_keccak.h"
 #include "crypto/c_groestl.h"
diff --git a/src/crypto/flex/cryptonote/cryptonight_turtle_lite.c b/src/crypto/flex/cryptonote/cryptonight_turtle_lite.c
index dc73458c..af9983cd 100644
--- a/src/crypto/flex/cryptonote/cryptonight_turtle_lite.c
+++ b/src/crypto/flex/cryptonote/cryptonight_turtle_lite.c
@@ -6,6 +6,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include "crypto/oaes_lib.h"
 #include "crypto/c_keccak.h"
 #include "crypto/c_groestl.h"