diff --git a/src/pipe/graph-history.h b/src/pipe/graph-history.h
index 48b4056c..121d07e8 100644
--- a/src/pipe/graph-history.h
+++ b/src/pipe/graph-history.h
@@ -34,7 +34,7 @@ dt_graph_history_reset(
   // write all connections
   for(uint32_t m=0;m<graph->num_modules;m++)
     for(int c=0;c<graph->module[m].num_connectors;c++,i+=(hi[i+1]!=hi[i]))
-      if(!(hi[i+1] = dt_graph_write_connection_ascii(graph, m, c, hi[i], max-hi[i])))
+      if(!(hi[i+1] = dt_graph_write_connection_ascii(graph, m, c, hi[i], max-hi[i], 1)))
         return 1;
 
   // write all params
@@ -130,7 +130,7 @@ dt_graph_history_connection(
   if(_dt_graph_history_check_buf(graph, 70)) return;
   int i = graph->history_item_end;
   char **hi = graph->history_item, *max = graph->history_pool + graph->history_max;
-  if(hi[i] < (hi[i+1] = dt_graph_write_connection_ascii(graph, modid, conid, hi[i], max - hi[i])))
+  if(hi[i] < (hi[i+1] = dt_graph_write_connection_ascii(graph, modid, conid, hi[i], max - hi[i], 1)))
   { *(hi[i+1]-1) = 0; graph->history_item_cur = ++graph->history_item_end; }
 }
 
diff --git a/src/pipe/graph-io.c b/src/pipe/graph-io.c
index fc2283e8..0f4e96b6 100644
--- a/src/pipe/graph-io.c
+++ b/src/pipe/graph-io.c
@@ -340,7 +340,8 @@ dt_graph_write_connection_ascii(
     const int         m,      // module index
     const int         i,      // connector index on given module
     char             *line,
-    size_t            size)
+    size_t            size,
+    int               allow_empty)
 {
   if(graph->module[m].name == 0) return line;
   dt_connector_t *c = graph->module[m].connector+i;
@@ -348,6 +349,7 @@ dt_graph_write_connection_ascii(
   dt_token_t name, inst, conn;
   if(c->connected_mi == -1)
   { // explicitly record disconnect event (important for history)
+    if(!allow_empty) return line; // don't write disconnect events explicitly
     name = inst = conn = dt_token("-1");
   }
   else
@@ -490,7 +492,7 @@ int dt_graph_write_config_ascii(
   // write all connections
   for(int m=0;m<graph->num_modules;m++)
     for(int i=0;i<graph->module[m].num_connectors;i++)
-      if(!(buf = dt_graph_write_connection_ascii(graph, m, i, buf, end-buf)))
+      if(!(buf = dt_graph_write_connection_ascii(graph, m, i, buf, end-buf, 0)))
         goto error;
 
   // write all params
diff --git a/src/pipe/graph-io.h b/src/pipe/graph-io.h
index a0313a1f..168c0064 100644
--- a/src/pipe/graph-io.h
+++ b/src/pipe/graph-io.h
@@ -26,7 +26,8 @@ dt_graph_write_connection_ascii(
     const int         m,      // module index
     const int         i,      // connector index on given module
     char             *line,
-    size_t            size);
+    size_t            size,
+    int               write_empty); // also serialise disconnected inputs (for history)
 
 // write param
 VKDT_API char *
diff --git a/src/pipe/modules/bs.h b/src/pipe/modules/bs.h
index 2b2021e4..427f5355 100644
--- a/src/pipe/modules/bs.h
+++ b/src/pipe/modules/bs.h
@@ -26,7 +26,7 @@ DECLARE_FUNC(int,   dt_module_connect,  (dt_graph_t *graph, int n0, int c0, int
 DECLARE_FUNC(int,   dt_module_feedback, (dt_graph_t *graph, int n0, int c0, int n1, int c1));
 DECLARE_FUNC(int,   dt_module_remove,   (dt_graph_t *graph, const int mid));
 DECLARE_FUNC(int,   dt_module_add,      (dt_graph_t *graph, dt_token_t name, dt_token_t inst));
-DECLARE_FUNC(char*, dt_graph_write_connection_ascii, (dt_graph_t *graph, const int m, const int i, char *line, size_t size));
+DECLARE_FUNC(char*, dt_graph_write_connection_ascii, (dt_graph_t *graph, const int m, const int i, char *line, size_t size, int allow_empty));
 DECLARE_FUNC(char*, dt_graph_write_param_ascii,  (const dt_graph_t *graph, const int m, const int p, char *line, size_t size, char **eop));
 DECLARE_FUNC(char*, dt_graph_write_module_ascii, (const dt_graph_t *graph, const int m, char *line, size_t size));
 DECLARE_VAR(dt_pipe_global_t, dt_pipe);