diff --git a/mod_entropy.c b/mod_entropy.c
index c1c973b..9a4683b 100644
--- a/mod_entropy.c
+++ b/mod_entropy.c
@@ -42,7 +42,7 @@
 #include <time.h>
 
 
-int add_entropy(unsigned char *, size_t);
+int add_entropy(const unsigned char *, size_t);
 
 module AP_MODULE_DECLARE_DATA entropy_module;
 
diff --git a/mod_entropy_add_entropy.c b/mod_entropy_add_entropy.c
index c5f2a5a..713c32f 100644
--- a/mod_entropy_add_entropy.c
+++ b/mod_entropy_add_entropy.c
@@ -24,12 +24,13 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdio.h>
 #include <linux/random.h>
 #include <sys/ioctl.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 
-int get_entropy_bits(unsigned char *, size_t);
+int get_entropy_bits(const unsigned char *, size_t);
 
 /**
  * fill /dev/random with sha1 from current request
diff --git a/mod_entropy_get_entropy_bits.c b/mod_entropy_get_entropy_bits.c
index 54e73bf..1351c2c 100644
--- a/mod_entropy_get_entropy_bits.c
+++ b/mod_entropy_get_entropy_bits.c
@@ -20,6 +20,7 @@
  */
 
 #include <math.h>
+#include <sys/types.h>
 
 #define min(x, y)    ((x)<(y)?(x):(y))