Index: src/OFBlock.m
==================================================================
--- src/OFBlock.m
+++ src/OFBlock.m
@@ -233,10 +233,13 @@
 void
 _Block_object_assign(void *dst_, const void *src_, const int flags_)
 {
 	int flags = flags_ & (OF_BLOCK_FIELD_IS_BLOCK |
 	    OF_BLOCK_FIELD_IS_OBJECT | OF_BLOCK_FIELD_IS_BYREF);
+
+	if (src_ == NULL)
+		return;
 
 	switch (flags) {
 	case OF_BLOCK_FIELD_IS_BLOCK:
 		*(of_block_literal_t**)dst_ = _Block_copy(src_);
 		break;
@@ -273,10 +276,13 @@
 void
 _Block_object_dispose(const void *obj_, const int flags_)
 {
 	const int flags = flags_ & (OF_BLOCK_FIELD_IS_BLOCK |
 	    OF_BLOCK_FIELD_IS_OBJECT | OF_BLOCK_FIELD_IS_BYREF);
+
+	if (obj_ == NULL)
+		return;
 
 	switch (flags) {
 	case OF_BLOCK_FIELD_IS_BLOCK:
 		_Block_release(obj_);
 		break;