diff --git a/ext/mysql2_ext.c b/ext/mysql2_ext.c
index ef97a00..95491f6 100644
--- a/ext/mysql2_ext.c
+++ b/ext/mysql2_ext.c
@@ -175,7 +175,7 @@ static VALUE rb_mysql_client_init(RB_MYSQL_UNUSED int argc, RB_MYSQL_UNUSED VALU
   return self;
 }
 
-void rb_mysql_client_free(void * client) {
+static void rb_mysql_client_free(void * client) {
   MYSQL * c = client;
   if (c) {
     /*
@@ -366,7 +366,7 @@ static VALUE rb_mysql_result_to_obj(MYSQL_RES * r) {
   return obj;
 }
 
-void rb_mysql_result_free(void * wrapper) {
+static void rb_mysql_result_free(void * wrapper) {
   mysql2_result_wrapper * w = wrapper;
   if (w && w->resultFreed != 1) {
     /* FIXME: this may call flush_use_result, which can hit the socket */
@@ -375,7 +375,7 @@ void rb_mysql_result_free(void * wrapper) {
   }
 }
 
-void rb_mysql_result_mark(void * wrapper) {
+static void rb_mysql_result_mark(void * wrapper) {
     mysql2_result_wrapper * w = wrapper;
     if (w) {
         rb_gc_mark(w->fields);
@@ -649,4 +649,4 @@ void Init_mysql2_ext() {
   utf8Encoding = rb_enc_find_index("UTF-8");
   binaryEncoding = rb_enc_find_index("binary");
 #endif
-}
\ No newline at end of file
+}
diff --git a/ext/mysql2_ext.h b/ext/mysql2_ext.h
index e576a31..77005e6 100644
--- a/ext/mysql2_ext.h
+++ b/ext/mysql2_ext.h
@@ -14,7 +14,7 @@
 
 #ifdef HAVE_RUBY_ENCODING_H
 #include <ruby/encoding.h>
-int utf8Encoding, binaryEncoding;
+static int utf8Encoding, binaryEncoding;
 #endif
 
 #if defined(__GNUC__) && (__GNUC__ >= 3)
@@ -24,10 +24,10 @@ int utf8Encoding, binaryEncoding;
 #endif
 
 static VALUE cBigDecimal, cDate, cDateTime;
-ID intern_new, intern_local;
+static ID intern_new, intern_local;
 
 /* Mysql2::Error */
-VALUE cMysql2Error;
+static VALUE cMysql2Error;
 
 /* Mysql2::Client */
 #define GetMysql2Client(obj, sval) (sval = (MYSQL*)DATA_PTR(obj));
@@ -45,7 +45,7 @@ static VALUE rb_mysql_client_socket(VALUE self);
 static VALUE rb_mysql_client_async_result(VALUE self);
 static VALUE rb_mysql_client_last_id(VALUE self);
 static VALUE rb_mysql_client_affected_rows(VALUE self);
-void rb_mysql_client_free(void * client);
+static void rb_mysql_client_free(void * client);
 
 /* Mysql2::Result */
 typedef struct {
@@ -58,12 +58,12 @@ typedef struct {
     MYSQL_RES *result;
 } mysql2_result_wrapper;
 #define GetMysql2Result(obj, sval) (sval = (mysql2_result_wrapper*)DATA_PTR(obj));
-VALUE cMysql2Result;
+static VALUE cMysql2Result;
 static VALUE rb_mysql_result_to_obj(MYSQL_RES * res);
 static VALUE rb_mysql_result_fetch_row(int argc, VALUE * argv, VALUE self);
 static VALUE rb_mysql_result_each(int argc, VALUE * argv, VALUE self);
-void rb_mysql_result_free(void * wrapper);
-void rb_mysql_result_mark(void * wrapper);
+static void rb_mysql_result_free(void * wrapper);
+static void rb_mysql_result_mark(void * wrapper);
 
 /*
  * used to pass all arguments to mysql_real_connect while inside
@@ -113,4 +113,4 @@ rb_thread_blocking_region(
 
 	return rv;
 }
-#endif /* ! HAVE_RB_THREAD_BLOCKING_REGION */
\ No newline at end of file
+#endif /* ! HAVE_RB_THREAD_BLOCKING_REGION */