diff --git a/ast.cpp b/ast.cpp
index 7f601d04..445ef4c7 100644
--- a/ast.cpp
+++ b/ast.cpp
@@ -307,19 +307,39 @@ TypeCheck(Stmt *stmt) {
 }
 
 
+struct CostData {
+    CostData() { cost = foreachDepth = 0; }
+
+    int cost;
+    int foreachDepth;
+};
+
+
 static bool
-lCostCallback(ASTNode *node, void *c) {
-    int *cost = (int *)c;
-    *cost += node->EstimateCost();
+lCostCallbackPre(ASTNode *node, void *d) {
+    CostData *data = (CostData *)d;
+    if (dynamic_cast<ForeachStmt *>(node) != NULL)
+        ++data->foreachDepth;
+    if (data->foreachDepth == 0)
+        data->cost += node->EstimateCost();
     return true;
 }
 
 
+static ASTNode *
+lCostCallbackPost(ASTNode *node, void *d) {
+    CostData *data = (CostData *)d;
+    if (dynamic_cast<ForeachStmt *>(node) != NULL)
+        --data->foreachDepth;
+    return node;
+}
+
+
 int
 EstimateCost(ASTNode *root) {
-    int cost = 0;
-    WalkAST(root, lCostCallback, NULL, &cost);
-    return cost;
+    CostData data;
+    WalkAST(root, lCostCallbackPre, lCostCallbackPost, &data);
+    return data.cost;
 }