diff -urN rpm-4_0-4.0.4-orig/build/parseSpec.c rpm-4_0-4.0.4/build/parseSpec.c
--- rpm-4_0-4.0.4-orig/build/parseSpec.c	2005-10-13 03:55:57 +0400
+++ rpm-4_0-4.0.4/build/parseSpec.c	2005-10-25 13:51:34 +0400
@@ -676,7 +676,7 @@
     /*@-infloops@*/	/* LCL: parsePart is modified @*/
     while (parsePart < PART_LAST && parsePart != PART_NONE) {
 	rpmBuiltinMacroLookup saved_lookup = rpmSetBuiltinMacroLookup(NULL);
-	int saved_lookup_failed = rpmSetBuiltinMacroLookupFailedOK(rpmExpandNumeric("%{?_allow_undefined_macros}"));
+	int saved_lookup_failed = rpmSetBuiltinMacroLookupFailedOK(rpmExpandNumeric("%{?_allow_undefined_macros}") || preprocess);
 	switch (parsePart) {
 	case PART_PREAMBLE:
 	    rpmSetBuiltinMacroLookup(is_builtin_preamble_tag);