diff --git a/external/Box2D/Collision/Shapes/b2ChainShape.cpp b/external/Box2D/Collision/Shapes/b2ChainShape.cpp
index 069b4cae84..010b9edcb9 100644
--- a/external/Box2D/Collision/Shapes/b2ChainShape.cpp
+++ b/external/Box2D/Collision/Shapes/b2ChainShape.cpp
@@ -20,6 +20,7 @@
 #include <Box2D/Collision/Shapes/b2EdgeShape.h>
 #include <new>
 #include <memory.h>
+#include <string.h>
 
 b2ChainShape::~b2ChainShape()
 {
diff --git a/external/Box2D/Collision/b2DynamicTree.cpp b/external/Box2D/Collision/b2DynamicTree.cpp
index 7035ab8b84..2607c6beee 100644
--- a/external/Box2D/Collision/b2DynamicTree.cpp
+++ b/external/Box2D/Collision/b2DynamicTree.cpp
@@ -18,6 +18,7 @@
 
 #include <Box2D/Collision/b2DynamicTree.h>
 #include <memory.h>
+#include <string.h>
 
 b2DynamicTree::b2DynamicTree()
 {
diff --git a/external/Box2D/Common/b2BlockAllocator.cpp b/external/Box2D/Common/b2BlockAllocator.cpp
index f7a4688ea9..b09a968435 100644
--- a/external/Box2D/Common/b2BlockAllocator.cpp
+++ b/external/Box2D/Common/b2BlockAllocator.cpp
@@ -20,6 +20,7 @@
 #include <limits.h>
 #include <memory.h>
 #include <stddef.h>
+#include <string.h>
 
 int32 b2BlockAllocator::s_blockSizes[b2_blockSizes] = 
 {
diff --git a/external/Box2D/Common/b2GrowableStack.h b/external/Box2D/Common/b2GrowableStack.h
index 4094644a28..44813e3eab 100644
--- a/external/Box2D/Common/b2GrowableStack.h
+++ b/external/Box2D/Common/b2GrowableStack.h
@@ -20,6 +20,7 @@
 #define B2_GROWABLE_STACK_H
 #include <Box2D/Common/b2Settings.h>
 #include <memory.h>
+#include <string.h>
 
 /// This is a growable LIFO stack with an initial capacity of N.
 /// If the stack size exceeds the initial capacity, the heap is used