diff --git a/include/llvm/Support/Mangler.h b/include/llvm/Support/Mangler.h
index 5ad607dc774..502b7973439 100644
--- a/include/llvm/Support/Mangler.h
+++ b/include/llvm/Support/Mangler.h
@@ -8,6 +8,7 @@
 #define LLVM_SUPPORT_MANGLER_H
 
 class Value;
+class Module;
 #include <map>
 #include <set>