diff --git a/runtime/gc/allocator_type.h b/runtime/gc/allocator_type.h
index 992c32a..cd9f5d4 100644
--- a/runtime/gc/allocator_type.h
+++ b/runtime/gc/allocator_type.h
@@ -24,7 +24,7 @@
 
 // Different types of allocators.
 // Those marked with * have fast path entrypoints callable from generated code.
-enum AllocatorType {
+enum AllocatorType : char {
   // BumpPointer spaces are currently only used for ZygoteSpace construction.
   kAllocatorTypeBumpPointer,  // Use global CAS-based BumpPointer allocator. (*)
   kAllocatorTypeTLAB,  // Use TLAB allocator within BumpPointer space. (*)
diff --git a/runtime/mirror/array-alloc-inl.h b/runtime/mirror/array-alloc-inl.h
index 2ae4cab..eb083f7 100644
--- a/runtime/mirror/array-alloc-inl.h
+++ b/runtime/mirror/array-alloc-inl.h
@@ -25,6 +25,7 @@
 #include "base/bit_utils.h"
 #include "base/casts.h"
 #include "class.h"
+#include "gc/allocator_type.h"
 #include "gc/heap-inl.h"
 #include "obj_ptr-inl.h"
 #include "runtime.h"
diff --git a/runtime/mirror/array.h b/runtime/mirror/array.h
index 1ee4e50..f0397b6 100644
--- a/runtime/mirror/array.h
+++ b/runtime/mirror/array.h
@@ -19,12 +19,15 @@
 
 #include "base/bit_utils.h"
 #include "base/enums.h"
-#include "gc/allocator_type.h"
 #include "obj_ptr.h"
 #include "object.h"
 
 namespace art {
 
+namespace gc {
+enum AllocatorType : char;
+}  // namespace gc
+
 template<class T> class Handle;
 class Thread;
 
diff --git a/runtime/mirror/class-alloc-inl.h b/runtime/mirror/class-alloc-inl.h
index d4a532e..03c422f 100644
--- a/runtime/mirror/class-alloc-inl.h
+++ b/runtime/mirror/class-alloc-inl.h
@@ -19,6 +19,7 @@
 
 #include "class-inl.h"
 
+#include "gc/allocator_type.h"
 #include "gc/heap-inl.h"
 #include "object-inl.h"
 #include "runtime.h"
diff --git a/runtime/mirror/class.h b/runtime/mirror/class.h
index d09b484..f2ba7d0 100644
--- a/runtime/mirror/class.h
+++ b/runtime/mirror/class.h
@@ -26,7 +26,6 @@
 #include "dex/dex_file_types.h"
 #include "dex/modifiers.h"
 #include "dex/primitive.h"
-#include "gc/allocator_type.h"
 #include "object.h"
 #include "object_array.h"
 #include "read_barrier_option.h"
@@ -38,6 +37,10 @@
 class TypeList;
 }  // namespace dex
 
+namespace gc {
+enum AllocatorType : char;
+}  // namespace gc
+
 namespace hiddenapi {
 class AccessContext;
 }  // namespace hiddenapi
diff --git a/runtime/mirror/string-alloc-inl.h b/runtime/mirror/string-alloc-inl.h
index 7215c39..32b6bb4 100644
--- a/runtime/mirror/string-alloc-inl.h
+++ b/runtime/mirror/string-alloc-inl.h
@@ -24,6 +24,7 @@
 #include "base/bit_utils.h"
 #include "class.h"
 #include "class_root.h"
+#include "gc/allocator_type.h"
 #include "gc/heap-inl.h"
 #include "obj_ptr.h"
 #include "runtime.h"
diff --git a/runtime/mirror/string.h b/runtime/mirror/string.h
index c98aa6b..6b7dfd5 100644
--- a/runtime/mirror/string.h
+++ b/runtime/mirror/string.h
@@ -18,13 +18,16 @@
 #define ART_RUNTIME_MIRROR_STRING_H_
 
 #include "base/bit_utils.h"
-#include "gc/allocator_type.h"
 #include "class.h"
 #include "object.h"
 #include "runtime_globals.h"
 
 namespace art {
 
+namespace gc {
+enum AllocatorType : char;
+}  // namespace gc
+
 template<class T> class Handle;
 template<class MirrorType> class ObjPtr;
 struct StringOffsets;