diff --git a/c/riscos b/c/riscos
index 1eee9fbeaa3397c8e70b2144cffaf6b19ff8ff23..3978ead93951003fbd9f95a4545621e4f90767d1 100644
--- a/c/riscos
+++ b/c/riscos
@@ -108,7 +108,7 @@ int encoding__load_map_file(const char *leaf, UCS2 **ptable, int *pn_entries, in
     return table != NULL;
 }
 
-int encoding_current_alphabet()
+int encoding_current_alphabet(void)
 {
     int a = 0;