diff --git a/toolchain/check/cpp/context.cpp b/toolchain/check/cpp/context.cpp
index ccf3e6e08a8b..4891ec6f4126 100644
--- a/toolchain/check/cpp/context.cpp
+++ b/toolchain/check/cpp/context.cpp
@@ -4,6 +4,7 @@
 
 #include "toolchain/check/cpp/context.h"
 
+#include "clang/AST/ASTContext.h"
 #include "clang/AST/Mangle.h"
 #include "clang/Frontend/CompilerInstance.h"