diff --git a/preprocess.c b/preprocess.c
index b19b8a4b02c2b4539dd4c646cbae02b58d0f8801..4f295d1eb94a8d41668b087fc2877c7609c2dd8d 100644
--- a/preprocess.c
+++ b/preprocess.c
@@ -53,10 +53,16 @@ static Token *append(Token *tok1, Token *tok2) {
 }
 
 // Skip until next `#endif`.
+// Nested `#if` and `#endif` are skipped.
 static Token *skip_cond_incl(Token *tok) {
   while (tok->kind != TK_EOF) {
+    if (is_hash(tok) && equal(tok->next, "if")) {
+      tok = skip_cond_incl(tok->next->next);
+      tok = tok->next;
+      continue;
+    }
     if (is_hash(tok) && equal(tok->next, "endif"))
-      return tok;
+      break;
     tok = tok->next;
   }
   return tok;
diff --git a/test/macro.c b/test/macro.c
index dd8262b8c113eb94c676519fd41cba816b4d7e35..999838223200d66803aa876c9b531e3853f1fc01 100644
--- a/test/macro.c
+++ b/test/macro.c
@@ -17,6 +17,8 @@ int main() {
 #if 0
 #include "/no/such/file"
   assert(0, 1, "1");
+#if nested
+#endif
 #endif
 
   int m = 0;