Index: src/OFBlock.m
==================================================================
--- src/OFBlock.m
+++ src/OFBlock.m
@@ -238,10 +238,13 @@
 	int flags = flags_ & (OF_BLOCK_FIELD_IS_BLOCK |
 	    OF_BLOCK_FIELD_IS_OBJECT | OF_BLOCK_FIELD_IS_BYREF);
 
 	if (src_ == NULL)
 		return;
+
+	if (flags_ & OF_BLOCK_BYREF_CALLER)
+		return;
 
 	switch (flags) {
 	case OF_BLOCK_FIELD_IS_BLOCK:
 		*(of_block_literal_t**)dst_ = _Block_copy(src_);
 		break;
@@ -281,10 +284,13 @@
 	const int flags = flags_ & (OF_BLOCK_FIELD_IS_BLOCK |
 	    OF_BLOCK_FIELD_IS_OBJECT | OF_BLOCK_FIELD_IS_BYREF);
 
 	if (obj_ == NULL)
 		return;
+
+	if (flags_ & OF_BLOCK_BYREF_CALLER)
+		return;
 
 	switch (flags) {
 	case OF_BLOCK_FIELD_IS_BLOCK:
 		_Block_release(obj_);
 		break;