Index: dispatcher.cpp
===================================================================
--- dispatcher.cpp	(revision 3033)
+++ dispatcher.cpp	(working copy)
@@ -1604,19 +1604,22 @@
     std::map<void *, rb_vm_block_t *>::iterator iter = blocks.find(key);

     rb_vm_block_t *b;
+    int alloc_mask = VM_BLOCK_ACTIVE | VM_BLOCK_PROC | VM_BLOCK_IFUNC;

-    if ((iter == blocks.end())
-	|| (iter->second->flags & (VM_BLOCK_ACTIVE | VM_BLOCK_PROC))) {
+    if ((iter == blocks.end()) || (iter->second->flags & alloc_mask)) {
+	bool is_ifunc = (iter != blocks.end())
+	    && ((iter->second->flags & VM_BLOCK_IFUNC) == VM_BLOCK_IFUNC);

-	if (iter != blocks.end()) {
+	if (is_ifunc == false && iter != blocks.end()) {
 	    rb_objc_release(iter->second);
 	}
-
 	b = (rb_vm_block_t *)xmalloc(sizeof(rb_vm_block_t)
 		+ (sizeof(VALUE *) * dvars_size));
-	rb_objc_retain(b);
+	if (is_ifunc == false) {
+	    rb_objc_retain(b);
+	    blocks[key] = b;
+	}

-	blocks[key] = b;
 	*cached = false;
     }
     else {