diff --git a/t/t.h b/t/t.h
index ff123ae..0b0ae03 100644
--- a/t/t.h
+++ b/t/t.h
@@ -57,6 +57,7 @@ void t_verbose_hex(const uint8_t *, size_t);
 void t_verbose(const char *, ...)
 	CRYB_PRINTF(1, 2);
 
+#ifdef _IONBF /* proxy for <stdio.h> */
 /*
  * Convenience functions for temp files
  */
@@ -74,6 +75,7 @@ int t_feof(struct t_file *);
 void t_frewind(struct t_file *);
 void t_fclose(struct t_file *);
 void t_fcloseall(void);
+#endif
 
 /*
  * Various utilities
diff --git a/t/t_const.c b/t/t_const.c
index 10f58c2..743312f 100644
--- a/t/t_const.c
+++ b/t/t_const.c
@@ -30,7 +30,7 @@
 #include "cryb/impl.h"
 
 #include <stdint.h>
-#include <stdio.h>
+#include <stdlib.h>
 
 #include "t.h"
 
diff --git a/t/t_hmac_sha1.c b/t/t_hmac_sha1.c
index e373a4c..dae8c97 100644
--- a/t/t_hmac_sha1.c
+++ b/t/t_hmac_sha1.c
@@ -32,7 +32,6 @@
 
 #include <err.h>
 #include <stdint.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/t/t_hmac_sha224.c b/t/t_hmac_sha224.c
index 641ba1e..7a9d13f 100644
--- a/t/t_hmac_sha224.c
+++ b/t/t_hmac_sha224.c
@@ -32,7 +32,6 @@
 
 #include <err.h>
 #include <stdint.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/t/t_hmac_sha256.c b/t/t_hmac_sha256.c
index efc76a7..26d7ef7 100644
--- a/t/t_hmac_sha256.c
+++ b/t/t_hmac_sha256.c
@@ -32,7 +32,6 @@
 
 #include <err.h>
 #include <stdint.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/t/t_hmac_sha384.c b/t/t_hmac_sha384.c
index 39f3551..a86e798 100644
--- a/t/t_hmac_sha384.c
+++ b/t/t_hmac_sha384.c
@@ -32,7 +32,6 @@
 
 #include <err.h>
 #include <stdint.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/t/t_hmac_sha512.c b/t/t_hmac_sha512.c
index 9c4afa5..421b16a 100644
--- a/t/t_hmac_sha512.c
+++ b/t/t_hmac_sha512.c
@@ -32,7 +32,6 @@
 
 #include <err.h>
 #include <stdint.h>
-#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
diff --git a/t/t_murmur3_32.c b/t/t_murmur3_32.c
index c9c89c8..250093e 100644
--- a/t/t_murmur3_32.c
+++ b/t/t_murmur3_32.c
@@ -30,7 +30,6 @@
 #include "cryb/impl.h"
 
 #include <stdint.h>
-#include <stdio.h>
 #include <string.h>
 
 #include <cryb/hash.h>
diff --git a/t/t_pearson.c b/t/t_pearson.c
index e80ea8f..fd4b921 100644
--- a/t/t_pearson.c
+++ b/t/t_pearson.c
@@ -30,7 +30,6 @@
 #include "cryb/impl.h"
 
 #include <stdint.h>
-#include <stdio.h>
 #include <string.h>
 
 #include <cryb/hash.h>
diff --git a/t/t_string.c b/t/t_string.c
index d29d8d9..4eb7cba 100644
--- a/t/t_string.c
+++ b/t/t_string.c
@@ -30,7 +30,6 @@
 #include "cryb/impl.h"
 
 #include <stdint.h>
-#include <stdio.h>
 #include <string.h>
 
 #include <cryb/string.h>
diff --git a/t/t_strlcat.c b/t/t_strlcat.c
index 18dbf58..87ba01c 100644
--- a/t/t_strlcat.c
+++ b/t/t_strlcat.c
@@ -30,7 +30,6 @@
 #include "cryb/impl.h"
 
 #include <stdint.h>
-#include <stdio.h>
 #include <string.h>
 
 #undef HAVE_STRLCAT
diff --git a/t/t_strlcpy.c b/t/t_strlcpy.c
index 8220a46..2244c1c 100644
--- a/t/t_strlcpy.c
+++ b/t/t_strlcpy.c
@@ -30,7 +30,6 @@
 #include "cryb/impl.h"
 
 #include <stdint.h>
-#include <stdio.h>
 #include <string.h>
 
 #undef HAVE_STRLCPY
diff --git a/t/t_wstring.c b/t/t_wstring.c
index ff3c7bd..e4a332d 100644
--- a/t/t_wstring.c
+++ b/t/t_wstring.c
@@ -30,7 +30,6 @@
 #include "cryb/impl.h"
 
 #include <stdint.h>
-#include <stdio.h>
 #include <string.h>
 #include <wchar.h>