diff --git a/src/add-ons/accelerants/matrox/InitAccelerant.c b/src/add-ons/accelerants/matrox/InitAccelerant.c
index 4af18f4773..377e89aacb 100644
--- a/src/add-ons/accelerants/matrox/InitAccelerant.c
+++ b/src/add-ons/accelerants/matrox/InitAccelerant.c
@@ -10,6 +10,7 @@
 #define MODULE_BIT 0x00800000
 
 #include <string.h>
+#include <unistd.h>
 #include "acc_std.h"
 
 /* defined in ProposeDisplayMode.c */
diff --git a/src/add-ons/accelerants/neomagic/InitAccelerant.c b/src/add-ons/accelerants/neomagic/InitAccelerant.c
index 835ff65060..b58668e727 100644
--- a/src/add-ons/accelerants/neomagic/InitAccelerant.c
+++ b/src/add-ons/accelerants/neomagic/InitAccelerant.c
@@ -10,6 +10,7 @@
 #define MODULE_BIT 0x00800000
 
 #include <string.h>
+#include <unistd.h>
 #include "acc_std.h"
 
 /* defined in ProposeDisplayMode.c */
diff --git a/src/add-ons/accelerants/nvidia/InitAccelerant.c b/src/add-ons/accelerants/nvidia/InitAccelerant.c
index f929580682..dd4b29289f 100644
--- a/src/add-ons/accelerants/nvidia/InitAccelerant.c
+++ b/src/add-ons/accelerants/nvidia/InitAccelerant.c
@@ -10,6 +10,7 @@
 #define MODULE_BIT 0x00800000
 
 #include <string.h>
+#include <unistd.h>
 #include "acc_std.h"
 
 /* defined in ProposeDisplayMode.c */