diff --git a/Makefile b/Makefile
index fd39b03..5fb5223 100644
--- a/Makefile
+++ b/Makefile
@@ -25,7 +25,7 @@ ifeq ("$(origin LD)", "default")
     undefine LD
 endif
 
-CFLAGS = -Wall -Werror
+CFLAGS = -Wall -Werror -Wmissing-prototypes
 # memcr CFLAGS
 MCFLAGS = $(CFLAGS) -g
 # parasite CFLAGS
diff --git a/arch/arm/cpu.c b/arch/arm/cpu.c
index 55b1e8f..cf42eef 100644
--- a/arch/arm/cpu.c
+++ b/arch/arm/cpu.c
@@ -21,7 +21,7 @@
 #include <sys/user.h>
 #include <assert.h>
 
-#include "cpu.h"
+#include "../cpu.h"
 
 void set_cpu_regs(struct registers *regs, unsigned long *pc, unsigned long arg0, unsigned long arg1)
 {
diff --git a/arch/arm64/cpu.c b/arch/arm64/cpu.c
index fa6d089..75103d9 100644
--- a/arch/arm64/cpu.c
+++ b/arch/arm64/cpu.c
@@ -21,7 +21,7 @@
 #include <sys/user.h>
 #include <assert.h>
 
-#include "cpu.h"
+#include "../cpu.h"
 
 void set_cpu_regs(struct registers *regs, unsigned long *pc, unsigned long arg0, unsigned long arg1)
 {
diff --git a/arch/syscall.c b/arch/syscall.c
index 508609e..e5e33d9 100644
--- a/arch/syscall.c
+++ b/arch/syscall.c
@@ -30,6 +30,8 @@
 #error unsupported arch
 #endif
 
+#include "syscall.h"
+
 ssize_t sys_read(int fd, void *buf, size_t count)
 {
 	return syscall3(__NR_read, fd, (unsigned long)buf, count);
diff --git a/arch/syscall.h b/arch/syscall.h
index 4317804..d17a925 100644
--- a/arch/syscall.h
+++ b/arch/syscall.h
@@ -22,7 +22,7 @@
 ssize_t sys_read(int fd, void *buf, size_t count);
 ssize_t sys_write(int fd, const void *buf, size_t count);
 int sys_close(int fd);
-int sys_mprotect(unsigned long addr, size_t len, int prot);
+int sys_mprotect(unsigned long addr, size_t len, unsigned long prot);
 int sys_madvise(unsigned long addr, size_t len, int advice);
 int sys_socket(int family, int type, int protocol);
 int sys_accept(int fd, struct sockaddr *addr, socklen_t *addrlen);
diff --git a/arch/x86_64/cpu.c b/arch/x86_64/cpu.c
index b0248fc..fc06782 100644
--- a/arch/x86_64/cpu.c
+++ b/arch/x86_64/cpu.c
@@ -20,7 +20,7 @@
 #include <sys/user.h>
 #include <assert.h>
 
-#include "cpu.h"
+#include "../cpu.h"
 
 void set_cpu_regs(struct registers *regs, unsigned long *pc, unsigned long arg0, unsigned long arg1)
 {
diff --git a/arch/x86_64/enter.c b/arch/x86_64/enter.c
index a583cbc..25eb5e4 100644
--- a/arch/x86_64/enter.c
+++ b/arch/x86_64/enter.c
@@ -16,12 +16,11 @@
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
  */
 
-#define _GNU_SOURCE
 #include <signal.h>
 #include <sys/mman.h>
-#include <sched.h>
+#include <linux/sched.h>
 
-void __attribute__((used)) container(void)
+static void __attribute__((used)) container(void)
 {
 	/*
 	 * Upon completion, each blob triggers debug trap to pass the
diff --git a/libencrypt.c b/libencrypt.c
index 8cd4c27..db0d094 100644
--- a/libencrypt.c
+++ b/libencrypt.c
@@ -47,6 +47,16 @@ static int block_size;
 static unsigned char key[16];
 static unsigned char iv[16];
 
+/*
+ * Prototypes matching memcr.
+ */
+int lib__open(const char *pathname, int flags, mode_t mode);
+int lib__close(int fd);
+int lib__read(int fd, void *buf, size_t count);
+int lib__write(int fd, const void *buf, size_t count);
+int lib__init(int enable, const char *arg);
+int lib__fini(void);
+
 
 int lib__open(const char *pathname, int flags, mode_t mode)
 {
diff --git a/memcr.c b/memcr.c
index c9565fb..7251321 100644
--- a/memcr.c
+++ b/memcr.c
@@ -1759,7 +1759,7 @@ static int setup_parasite_args(pid_t pid, void *base)
 }
 
 
-void *parasite_watch_thread(void *ptr)
+static void *parasite_watch_thread(void *ptr)
 {
 	int ret;
 	unsigned long pid = (unsigned long)ptr;
@@ -1785,7 +1785,7 @@ void *parasite_watch_thread(void *ptr)
 	return NULL;
 }
 
-int parasite_watch(pid_t pid)
+static int parasite_watch(pid_t pid)
 {
 	int ret;
 	pthread_t id;
@@ -2225,7 +2225,7 @@ static void restore_procedure_service(int cd, struct service_command svc_cmd)
 	}
 }
 
-void register_signal_handlers()
+static void register_signal_handlers(void)
 {
 	struct sigaction sigchld_action, sigpipe_action;
 
@@ -2437,7 +2437,7 @@ static void usage(const char *name, int status)
 	exit(status);
 }
 
-void die(const char *fmt, ...)
+static void die(const char *fmt, ...)
 {
 	va_list ap;
 
diff --git a/parasite.c b/parasite.c
index 4b0150a..94d6f43 100644
--- a/parasite.c
+++ b/parasite.c
@@ -36,6 +36,8 @@
 
 static int finish;
 
+void service(unsigned int cmd, void *args);
+
 #if VERBOSE == 1
 static char *long_to_str(long v)
 {