diff --git a/object/string.c b/object/string.c
index 8d41f0f..893911a 100644
--- a/object/string.c
+++ b/object/string.c
@@ -211,7 +211,7 @@ b_status b_string_replace_all(b_string *str, const char *new_data)
 	return B_SUCCESS;
 }
 
-enum b_status stream_close(struct b_stream *stream)
+static enum b_status stream_close(struct b_stream *stream)
 {
 	struct b_string *str = stream->s_ptr;
 	b_string_release(str);
@@ -219,7 +219,7 @@ enum b_status stream_close(struct b_stream *stream)
 	return B_SUCCESS;
 }
 
-enum b_status stream_getc(struct b_stream *stream, int *out)
+static enum b_status stream_getc(struct b_stream *stream, int *out)
 {
 	struct b_string *str = stream->s_ptr;
 	if (stream->s_cursor >= str->s_len) {
@@ -233,7 +233,7 @@ enum b_status stream_getc(struct b_stream *stream, int *out)
 	return B_SUCCESS;
 }
 
-enum b_status stream_read(
+static enum b_status stream_read(
 	struct b_stream *stream, unsigned char *buf, size_t count, size_t *nr_read)
 {
 	struct b_string *str = stream->s_ptr;
@@ -254,7 +254,7 @@ enum b_status stream_read(
 	return B_SUCCESS;
 }
 
-enum b_status stream_write(
+static enum b_status stream_write(
 	struct b_stream *stream, const unsigned char *buf, size_t count,
 	size_t *nr_written)
 {
@@ -280,7 +280,7 @@ enum b_status stream_write(
 	return B_SUCCESS;
 }
 
-enum b_status stream_seek(
+static enum b_status stream_seek(
 	struct b_stream *stream, long long offset, b_stream_seek_origin origin)
 {
 	struct b_string *str = stream->s_ptr;
@@ -305,7 +305,7 @@ enum b_status stream_seek(
 	return B_SUCCESS;
 }
 
-enum b_status stream_reserve(struct b_stream *stream, size_t len)
+static enum b_status stream_reserve(struct b_stream *stream, size_t len)
 {
 	struct b_string *str = stream->s_ptr;