diff --git a/nasm.c b/nasm.c
index 63199c7a..e26d7b37 100644
--- a/nasm.c
+++ b/nasm.c
@@ -378,6 +378,8 @@ static int process_arg (char *p, char *q)
 	  case 'E':
 	  case 'F':
 	  case 'X':
+	  case 'u':
+	  case 'U':
 	    if ( !(param = get_param (p, q, &advance)) )
 		break;
 	    if (p[1]=='o') {	       /* output file */
diff --git a/preproc.c b/preproc.c
index 0770812e..abe92d0f 100644
--- a/preproc.c
+++ b/preproc.c
@@ -4429,6 +4429,7 @@ pp_pre_undefine(char *definition)
 
     space = new_Token(NULL, TOK_WHITESPACE, NULL, 0);
     def = new_Token(space, TOK_PREPROC_ID, "%undef", 0);
+    space->next = tokenise(definition);
 
     l = nasm_malloc(sizeof(Line));
     l->next = predef;