diff --git a/toolchain/semantics/BUILD b/toolchain/semantics/BUILD
index 87cbbd2f8a18..a2e14e088611 100644
--- a/toolchain/semantics/BUILD
+++ b/toolchain/semantics/BUILD
@@ -30,6 +30,7 @@ cc_library(
     deps = [
         "//common:check",
         "//toolchain/parser:parse_tree",
+        "@llvm-project//llvm:Support",
     ],
 )
 
diff --git a/toolchain/semantics/parse_subtree_consumer.h b/toolchain/semantics/parse_subtree_consumer.h
index 2ea8fc7363aa..439db1a4e38f 100644
--- a/toolchain/semantics/parse_subtree_consumer.h
+++ b/toolchain/semantics/parse_subtree_consumer.h
@@ -5,6 +5,9 @@
 #ifndef CARBON_TOOLCHAIN_SEMANTICS_PARSE_SUBTREE_CONSUMER_H_
 #define CARBON_TOOLCHAIN_SEMANTICS_PARSE_SUBTREE_CONSUMER_H_
 
+#include <iterator>
+
+#include "llvm/ADT/Optional.h"
 #include "toolchain/parser/parse_tree.h"
 
 namespace Carbon {