diff --git a/src/fm_server.cpp b/src/fm_server.cpp
index 40c7199b7..e2cd8e435 100644
--- a/src/fm_server.cpp
+++ b/src/fm_server.cpp
@@ -454,6 +454,9 @@ class AbmWorldThread : public thread_vector
 						return block;
 					};
 					auto *block = load_block(pos);
+					if (!block) {
+						continue;
+					}
 
 					// Load neighbours for better liquids flows
 					for (const auto &dir : g_6dirs) {