diff --git a/src/saveload/saveload.h b/src/saveload/saveload.h
--- a/src/saveload/saveload.h
+++ b/src/saveload/saveload.h
@@ -896,6 +896,7 @@ void WriteValue(void *ptr, VarType conv,
 void SlSetArrayIndex(uint index);
 int SlIterateArray();
 
+uint SlCalcConvMemLen(VarType conv);
 void SlAutolength(AutolengthProc *proc, void *arg);
 size_t SlGetFieldLength();
 void SlSetLength(size_t length);