diff --git a/include/llvm/AbstractTypeUser.h b/include/llvm/AbstractTypeUser.h
index 659c1b9b617..272560ff288 100644
--- a/include/llvm/AbstractTypeUser.h
+++ b/include/llvm/AbstractTypeUser.h
@@ -21,6 +21,7 @@
 #ifndef LLVM_ABSTRACT_TYPE_USER_H
 #define LLVM_ABSTRACT_TYPE_USER_H
 
+#include <assert.h>
 class Type;
 class DerivedType;