diff --git a/libfreerdp-core/ber.c b/libfreerdp-core/ber.c
index f62bccaf7..3cd611ce0 100644
--- a/libfreerdp-core/ber.c
+++ b/libfreerdp-core/ber.c
@@ -282,7 +282,7 @@ boolean ber_read_octet_string(STREAM* s, int* length)
  * @param length string length
  */
 
-void ber_write_octet_string(STREAM* s, uint8* oct_str, int length)
+void ber_write_octet_string(STREAM* s, const uint8* oct_str, int length)
 {
 	ber_write_universal_tag(s, BER_TAG_OCTET_STRING, false);
 	ber_write_length(s, length);
diff --git a/libfreerdp-core/ber.h b/libfreerdp-core/ber.h
index 8a4c0d946..5b2e1e924 100644
--- a/libfreerdp-core/ber.h
+++ b/libfreerdp-core/ber.h
@@ -70,7 +70,7 @@ int ber_skip_sequence(int length);
 int ber_skip_sequence_tag(int length);
 boolean ber_read_bit_string(STREAM* s, int* length, uint8* padding);
 boolean ber_read_octet_string(STREAM* s, int* length);
-void ber_write_octet_string(STREAM* s, uint8* oct_str, int length);
+void ber_write_octet_string(STREAM* s, const uint8* oct_str, int length);
 int ber_write_octet_string_tag(STREAM* s, int length);
 int ber_skip_octet_string(int length);
 boolean ber_read_boolean(STREAM* s, boolean* value);