diff --git a/src/include/rtt.h b/src/include/rtt.h
index 7d8f04a..dc8756a 100644
--- a/src/include/rtt.h
+++ b/src/include/rtt.h
@@ -1,3 +1,29 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * MIT License
+ *
+ * Copyright (c) 2021 Koen De Vleeschauwer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
 #ifndef RTT_H
 #define RTT_H
 #include <target.h>
@@ -29,6 +55,6 @@ struct rtt_channel_struct {
 extern struct rtt_channel_struct rtt_channel[MAX_RTT_CHAN];
 
 // true if target memory access does not work when target running
-extern bool target_no_background_memory_access(target *cur_target);
-extern void poll_rtt(target *cur_target);
+bool target_no_background_memory_access(target *cur_target);
+void poll_rtt(target *cur_target);
 #endif
diff --git a/src/include/rtt_if.h b/src/include/rtt_if.h
index 711be5e..a6f70d5 100644
--- a/src/include/rtt_if.h
+++ b/src/include/rtt_if.h
@@ -1,3 +1,29 @@
+/*
+ * This file is part of the Black Magic Debug project.
+ *
+ * MIT License
+ *
+ * Copyright (c) 2021 Koen De Vleeschauwer
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
 #ifndef RTT_IF_H
 #define RTT_IF_H
 /* rtt i/o to terminal */
@@ -22,15 +48,15 @@
 #endif
 
 /* hosted initialisation */
-extern int rtt_if_init(void);
+int rtt_if_init(void);
 /* hosted teardown */
-extern int rtt_if_exit(void);
+int rtt_if_exit(void);
 
 /* target to host: write len bytes from the buffer starting at buf. return number bytes written */
-extern uint32_t rtt_write(const char *buf, uint32_t len);
+uint32_t rtt_write(const char *buf, uint32_t len);
 /* host to target: read one character, non-blocking. return character, -1 if no character */
-extern int32_t rtt_getchar();
+int32_t rtt_getchar();
 /* host to target: true if no characters available for reading */
-extern bool rtt_nodata();
+bool rtt_nodata();
 
 #endif