1 files changed, 4 insertions, 0 deletions
diff --git a/sys/cmd/cc/lex.c b/sys/cmd/cc/lex.c
index 2a637da..6c57b3c 100644
--- a/sys/cmd/cc/lex.c
+++ b/sys/cmd/cc/lex.c
@@ -40,6 +40,7 @@ getnsbyte(Lexer *lx)
         if (b == EOF) {
             if (lx->io->link) {
                 popio(lx);
+                assert(lx->io);
                 b = getbyte(lx);
                 continue;
             } else
@@ -687,6 +688,9 @@ popio(Lexer *lx)
 {
     Io *prev;
 
+    assert(lx->io == C.io-1);
+    --C.io;
+
     prev = lx->io->link;
     freeio(lx->io);