diff --git a/src/zone-inl.h b/src/zone-inl.h
index 7e506e7cac..96b4b0d9cd 100644
--- a/src/zone-inl.h
+++ b/src/zone-inl.h
@@ -28,8 +28,11 @@
 #ifndef V8_ZONE_INL_H_
 #define V8_ZONE_INL_H_
 
-#include "isolate.h"
 #include "zone.h"
+
+#include "counters.h"
+#include "isolate.h"
+#include "utils.h"
 #include "v8-counters.h"
 
 namespace v8 {
diff --git a/src/zone.cc b/src/zone.cc
index 2d14d137ef..5f3296a67e 100644
--- a/src/zone.cc
+++ b/src/zone.cc
@@ -26,9 +26,9 @@
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #include "v8.h"
-
 #include "zone-inl.h"
-#include "splay-tree-inl.h"
+
+#include <string.h>
 
 namespace v8 {
 namespace internal {
diff --git a/src/zone.h b/src/zone.h
index 2ca3c4d369..0fe4c926be 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -29,6 +29,10 @@
 #define V8_ZONE_H_
 
 #include "allocation.h"
+#include "checks.h"
+#include "globals.h"
+#include "list.h"
+#include "splay-tree.h"
 
 namespace v8 {
 namespace internal {
@@ -42,6 +46,7 @@ enum ZoneScopeMode {
 };
 
 class Segment;
+class Isolate;
 
 // The Zone supports very fast allocation of small chunks of
 // memory. The chunks cannot be deallocated individually, but instead