diff --git a/src/gdbstub.c b/src/gdbstub.c
index efca53f74..dc638cd07 100644
--- a/src/gdbstub.c
+++ b/src/gdbstub.c
@@ -334,7 +334,7 @@ int      gdbstub_step = 0, gdbstub_next_asap = 0;
 uint64_t gdbstub_watch_pages[(((uint32_t) -1) >> (MEM_GRANULARITY_BITS + 6)) + 1];
 
 static void
-gdbstub_break()
+gdbstub_break(void)
 {
     /* Pause CPU execution as soon as possible. */
     if (gdbstub_step <= GDBSTUB_EXEC)
@@ -988,8 +988,13 @@ e14:
 
                 /* Add our supported features to the end. */
                 if (client->response_pos < (sizeof(client->response) - 1))
+#if (defined __amd64__ || defined _M_X64 || defined __aarch64__ || defined _M_ARM64)
                     client->response_pos += snprintf(&client->response[client->response_pos], sizeof(client->response) - client->response_pos,
                                                      "PacketSize=%lX;swbreak+;hwbreak+;qXfer:features:read+", sizeof(client->packet) - 1);
+#else
+                    client->response_pos += snprintf(&client->response[client->response_pos], sizeof(client->response) - client->response_pos,
+                                                     "PacketSize=%X;swbreak+;hwbreak+;qXfer:features:read+", sizeof(client->packet) - 1);
+#endif
                 break;
             } else if (!strcmp(client->response, "Xfer")) {
                 /* Read the transfer object. */
@@ -1627,7 +1632,7 @@ gdbstub_server_thread(void *priv)
 }
 
 void
-gdbstub_cpu_init()
+gdbstub_cpu_init(void)
 {
     /* Replace cpu_exec with our own function if the GDB stub is active. */
     if ((gdbstub_socket != -1) && (cpu_exec != gdbstub_cpu_exec)) {
@@ -1637,7 +1642,7 @@ gdbstub_cpu_init()
 }
 
 int
-gdbstub_instruction()
+gdbstub_instruction(void)
 {
     /* Check hardware breakpoints if any are present. */
     gdbstub_breakpoint_t *breakpoint = first_hwbreak;
@@ -1667,7 +1672,7 @@ gdbstub_instruction()
 }
 
 int
-gdbstub_int3()
+gdbstub_int3(void)
 {
     /* Check software breakpoints if any are present. */
     gdbstub_breakpoint_t *breakpoint = first_swbreak;
@@ -1744,7 +1749,7 @@ gdbstub_mem_access(uint32_t *addrs, int access)
 }
 
 void
-gdbstub_init()
+gdbstub_init(void)
 {
 #ifdef _WIN32
     WSAStartup(MAKEWORD(2, 2), &wsa);
@@ -1790,7 +1795,7 @@ gdbstub_init()
 }
 
 void
-gdbstub_close()
+gdbstub_close(void)
 {
     /* Stop if the GDB server hasn't initialized. */
     if (gdbstub_socket < 0)
diff --git a/src/include/86box/gdbstub.h b/src/include/86box/gdbstub.h
index 4b2f8630a..8ac83f625 100644
--- a/src/include/86box/gdbstub.h
+++ b/src/include/86box/gdbstub.h
@@ -53,12 +53,12 @@ enum {
 extern int      gdbstub_step, gdbstub_next_asap;
 extern uint64_t gdbstub_watch_pages[(((uint32_t) -1) >> (MEM_GRANULARITY_BITS + 6)) + 1];
 
-extern void gdbstub_cpu_init();
-extern int  gdbstub_instruction();
-extern int  gdbstub_int3();
+extern void gdbstub_cpu_init(void);
+extern int  gdbstub_instruction(void);
+extern int  gdbstub_int3(void);
 extern void gdbstub_mem_access(uint32_t *addrs, int access);
-extern void gdbstub_init();
-extern void gdbstub_close();
+extern void gdbstub_init(void);
+extern void gdbstub_close(void);
 
 #else