diff --git a/ChangeLog b/ChangeLog
index d27f23c..ecbb9ef 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Sep 21 17:22:45 2008  Minero Aoki  <aamine@loveruby.net>
+
+	* net/loveruby/cflat/compiler/CodeGenerator.java: lhs.memref may
+	  be null when lhs is extern variable.
+
 Sun Sep 21 05:43:28 2008  Minero Aoki  <aamine@loveruby.net>
 
 	* net/loveruby/cflat/compiler/CodeGenerator.java: optimize
diff --git a/net/loveruby/cflat/compiler/CodeGenerator.java b/net/loveruby/cflat/compiler/CodeGenerator.java
index 1c6142c..f9099db 100644
--- a/net/loveruby/cflat/compiler/CodeGenerator.java
+++ b/net/loveruby/cflat/compiler/CodeGenerator.java
@@ -860,7 +860,7 @@ public class CodeGenerator extends Visitor implements ASTLHSVisitor {
     //
 
     public void visit(AssignNode node) {
-        if (node.lhs().isConstantAddress()) {
+        if (node.lhs().isConstantAddress() && node.lhs().memref() != null) {
             compile(node.rhs());
             save(node.type(), reg("ax"), node.lhs().memref());
         }
@@ -881,7 +881,7 @@ public class CodeGenerator extends Visitor implements ASTLHSVisitor {
     }
 
     public void visit(OpAssignNode node) {
-        if (node.lhs().isConstantAddress()) {
+        if (node.lhs().isConstantAddress() && node.lhs().memref() != null) {
             // const += ANY
             compile(node.rhs());
             mov(reg("ax"), reg("cx"));