diff --git a/include/patty/ax25/frame.h b/include/patty/ax25/frame.h
index 72ea6b8..c848db8 100644
--- a/include/patty/ax25/frame.h
+++ b/include/patty/ax25/frame.h
@@ -106,17 +106,17 @@ typedef struct _patty_ax25_frame_xid_param {
 #pragma pack(pop)
 
 ssize_t patty_ax25_frame_decode_address(patty_ax25_frame *frame,
-                                        void *buf,
+                                        const void *buf,
                                         size_t len);
 
 ssize_t patty_ax25_frame_decode_control(patty_ax25_frame *frame,
                                         enum patty_ax25_frame_format format,
-                                        void *buf,
+                                        const void *buf,
                                         size_t offset,
                                         size_t len);
 
 ssize_t patty_ax25_frame_decode_xid(patty_ax25_params *params,
-                                    void *data,
+                                    const void *data,
                                     size_t offset,
                                     size_t len);
 
diff --git a/src/frame.c b/src/frame.c
index e5cde26..7dc65ed 100644
--- a/src/frame.c
+++ b/src/frame.c
@@ -6,7 +6,7 @@
 #include "config.h"
 
 static ssize_t decode_station(patty_ax25_addr *addr,
-                              void *data,
+                              const void *data,
                               size_t offset,
                               size_t len) {
     int i, space = 0;
@@ -45,7 +45,7 @@ error:
 }
 
 static ssize_t decode_hops(patty_ax25_frame *frame,
-                           void *data,
+                           const void *data,
                            size_t offset,
                            size_t len) {
     ssize_t start = offset;
@@ -93,7 +93,7 @@ error:
 }
 
 ssize_t patty_ax25_frame_decode_address(patty_ax25_frame *frame,
-                                        void *buf,
+                                        const void *buf,
                                         size_t len) {
      size_t offset = 0;
     ssize_t decoded;
@@ -174,10 +174,10 @@ static inline uint8_t decode_pf(uint16_t control,
 
 ssize_t patty_ax25_frame_decode_control(patty_ax25_frame *frame,
                                         enum patty_ax25_frame_format format,
-                                        void *data,
+                                        const void *data,
                                         size_t offset,
                                         size_t len) {
-    uint8_t *buf = data;
+    const uint8_t *buf = data;
     size_t start = offset;
 
     frame->control = 0;
@@ -258,7 +258,7 @@ ssize_t patty_ax25_frame_decode_control(patty_ax25_frame *frame,
             frame->proto   = buf[offset++];
 
         case PATTY_AX25_FRAME_TEST:
-            frame->info    = buf + offset;
+            frame->info    = (uint8_t *)buf + offset;
             frame->infolen = len - offset;
 
             offset = len;
@@ -311,7 +311,7 @@ static void save_xid_param(patty_ax25_params *params,
 }
 
 ssize_t decode_xid_group(patty_ax25_params *params,
-                         void *data,
+                         const void *data,
                          size_t offset,
                          size_t len) {
     patty_ax25_frame_xid_group *group = (patty_ax25_frame_xid_group *)
@@ -367,7 +367,7 @@ error:
 }
 
 ssize_t patty_ax25_frame_decode_xid(patty_ax25_params *params,
-                                    void *data,
+                                    const void *data,
                                     size_t offset,
                                     size_t len) {
     size_t start = offset;