diff --git a/src/cpp.h b/src/cpp.h
index 7fcca20dba76c173454268a89c4a662378305247..b629743ec79aa4509edd4e68853904e096fc4fa5 100644
--- a/src/cpp.h
+++ b/src/cpp.h
@@ -18,9 +18,9 @@ void PUSH_STRING(char *str,
 		 dynamic_buffer *buf);
 void free_one_define(struct hash_entry *h);
 void f_cpp(INT32 args);
-void init_cpp();
+void init_cpp(void);
 void add_predefine(char *s);
-void exit_cpp();
+void exit_cpp(void);
 /* Prototypes end here */
 
 #endif
diff --git a/src/lex.h b/src/lex.h
index df6a17815016ce0d110b09b3df3ae9762c3029ac..3432fc4016acd8f17b26aecabc18a40c038c4bdb 100644
--- a/src/lex.h
+++ b/src/lex.h
@@ -66,7 +66,7 @@ extern struct instr instrs[];
 /* Prototypes begin here */
 void exit_lex(void);
 struct reserved;
-void init_lex();
+void init_lex(void);
 char *low_get_f_name(int n,struct program *p);
 char *get_f_name(int n);
 char *get_token_name(int n);