diff --git a/src/messages.c b/src/messages.c
index 8787147..0e4ddf8 100644
--- a/src/messages.c
+++ b/src/messages.c
@@ -55,14 +55,14 @@ void print_error_fmt(const char *fmt, const char *arg) {
 }
 
 // Imprime versão e ajuda e retorna status.
-int print_usage(int status, char *prog_name) {
+int print_usage(int status, const char *prog_name) {
     FILE *stream = stderr;
     if (status == EXIT_SUCCESS) stream = stdout;
     fprintf(stream, MSG_USAGE, prog_name);
     return status;
 }
 
-int print_error_usage(const char *err, char *prog_name) {
+int print_error_usage(const char *err, const char *prog_name) {
         print_error(err);
         return print_usage(EXIT_FAILURE, prog_name);
 }
diff --git a/src/messages.h b/src/messages.h
index 8356267..8da6437 100644
--- a/src/messages.h
+++ b/src/messages.h
@@ -23,7 +23,7 @@ void print_error(const char *msg);
 void print_error_fmt(const char *fmt, const char *arg);
 
 // Impressão da ajuda
-int print_usage(int status, char *prog_name);
-int print_error_usage(const char *err, char *prog_name);
+int print_usage(int status, const char *prog_name);
+int print_error_usage(const char *err, const char *prog_name);
 
 #endif // MESSAGES_H