diff --git a/src/crypto/flex/cryptonote/cryptonight_dark.c b/src/crypto/flex/cryptonote/cryptonight_dark.c
index 32b019683..d96da1fcf 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 d2f482de1..9ff329d51 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 46f26aff8..41df800b5 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 d9be39cd9..6b0606901 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 571630734..aa4cd8501 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 dc73458c0..af9983cde 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"