diff --git a/t/t_memset_s.c b/t/t_memset_s.c
index 8dc6152..de39197 100644
--- a/t/t_memset_s.c
+++ b/t/t_memset_s.c
@@ -32,6 +32,7 @@
 #include <errno.h>
 #include <stdint.h>
 #include <string.h>
+#include <unistd.h>
 
 #undef HAVE_MEMSET_S
 #include <cryb/memset_s.h>
diff --git a/t/t_mpi.c b/t/t_mpi.c
index e96d2a3..b63f5fb 100644
--- a/t/t_mpi.c
+++ b/t/t_mpi.c
@@ -32,6 +32,7 @@
 #include <assert.h>
 #include <stdint.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <cryb/endian.h>
 #include <cryb/mpi.h>
diff --git a/t/t_murmur3_32.c b/t/t_murmur3_32.c
index 31c6128..5e924b3 100644
--- a/t/t_murmur3_32.c
+++ b/t/t_murmur3_32.c
@@ -31,6 +31,7 @@
 
 #include <stdint.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <cryb/hash.h>
 
diff --git a/t/t_pearson.c b/t/t_pearson.c
index 3af1dfa..21313ca 100644
--- a/t/t_pearson.c
+++ b/t/t_pearson.c
@@ -31,6 +31,7 @@
 
 #include <stdint.h>
 #include <string.h>
+#include <unistd.h>
 
 #include <cryb/hash.h>
 
diff --git a/t/t_strlcat.c b/t/t_strlcat.c
index 3a72fe0..f0450de 100644
--- a/t/t_strlcat.c
+++ b/t/t_strlcat.c
@@ -31,6 +31,7 @@
 
 #include <stdint.h>
 #include <string.h>
+#include <unistd.h>
 
 #undef HAVE_STRLCAT
 #include <cryb/strlcat.h>
diff --git a/t/t_strlcpy.c b/t/t_strlcpy.c
index ecee06d..defe9f6 100644
--- a/t/t_strlcpy.c
+++ b/t/t_strlcpy.c
@@ -31,6 +31,7 @@
 
 #include <stdint.h>
 #include <string.h>
+#include <unistd.h>
 
 #undef HAVE_STRLCPY
 #include <cryb/strlcpy.h>