diff --git a/passes/fsm/fsm.cc b/passes/fsm/fsm.cc
index 3b537ecd8..997558b85 100644
--- a/passes/fsm/fsm.cc
+++ b/passes/fsm/fsm.cc
@@ -59,6 +59,9 @@ struct FsmPass : public Pass {
 		log("    -expand, -norecode, -export, -nomap\n");
 		log("        enable or disable passes as indicated above\n");
 		log("\n");
+		log("    -fullexpand\n");
+		log("        call expand with -full option\n");
+		log("\n");
 		log("    -encoding type\n");
 		log("    -fm_set_fsm_file file\n");
 		log("    -encfile file\n");
@@ -71,6 +74,7 @@ struct FsmPass : public Pass {
 		bool flag_norecode = false;
 		bool flag_nodetect = false;
 		bool flag_expand = false;
+		bool flag_fullexpand = false;
 		bool flag_export = false;
 		std::string fm_set_fsm_file_opt;
 		std::string encfile_opt;
@@ -110,6 +114,10 @@ struct FsmPass : public Pass {
 				flag_expand = true;
 				continue;
 			}
+			if (arg == "-fullexpand") {
+				flag_fullexpand = true;
+				continue;
+			}
 			if (arg == "-export") {
 				flag_export = true;
 				continue;
@@ -126,8 +134,8 @@ struct FsmPass : public Pass {
 		Pass::call(design, "opt_clean");
 		Pass::call(design, "fsm_opt");
 
-		if (flag_expand) {
-			Pass::call(design, "fsm_expand");
+		if (flag_expand || flag_fullexpand) {
+			Pass::call(design, flag_fullexpand ? "fsm_expand -full" : "fsm_expand");
 			Pass::call(design, "opt_clean");
 			Pass::call(design, "fsm_opt");
 		}
diff --git a/passes/fsm/fsm_expand.cc b/passes/fsm/fsm_expand.cc
index 3ded3f377..e7b9dcf90 100644
--- a/passes/fsm/fsm_expand.cc
+++ b/passes/fsm/fsm_expand.cc
@@ -32,6 +32,8 @@ struct FsmExpand
 {
 	RTLIL::Module *module;
 	RTLIL::Cell *fsm_cell;
+	bool full_mode;
+
 	SigMap assign_map;
 	SigSet<RTLIL::Cell*, RTLIL::sort_by_name_id<RTLIL::Cell>> sig2driver, sig2user;
 	CellTypes ct;
@@ -45,6 +47,9 @@ struct FsmExpand
 
 	bool is_cell_merge_candidate(RTLIL::Cell *cell)
 	{
+		if (full_mode || cell->type == "$_MUX_")
+			return true;
+
 		if (cell->type == "$mux" || cell->type == "$pmux")
 			if (cell->getPort("\\A").size() < 2)
 				return true;
@@ -68,17 +73,6 @@ struct FsmExpand
 		if (new_signals.size() > 3)
 			return false;
 
-		if (cell->hasPort("\\Y")) {
-			new_signals.append(assign_map(cell->getPort("\\Y")));
-			new_signals.sort_and_unify();
-			new_signals.remove_const();
-			new_signals.remove(assign_map(fsm_cell->getPort("\\CTRL_IN")));
-			new_signals.remove(assign_map(fsm_cell->getPort("\\CTRL_OUT")));
-		}
-
-		if (new_signals.size() > 2)
-			return false;
-
 		return true;
 	}
 
@@ -200,13 +194,15 @@ struct FsmExpand
 		fsm_data.copy_to_cell(fsm_cell);
 	}
 
-	FsmExpand(RTLIL::Cell *cell, RTLIL::Design *design, RTLIL::Module *mod)
+	FsmExpand(RTLIL::Cell *cell, RTLIL::Design *design, RTLIL::Module *mod, bool full)
 	{
 		module = mod;
 		fsm_cell = cell;
+		full_mode = full;
 
 		assign_map.set(module);
 		ct.setup_internals();
+		ct.setup_stdcells();
 
 		for (auto &cell_it : module->cells_) {
 			RTLIL::Cell *c = cell_it.second;
@@ -249,17 +245,31 @@ struct FsmExpandPass : public Pass {
 	{
 		//   |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 		log("\n");
-		log("    fsm_expand [selection]\n");
+		log("    fsm_expand [-full] [selection]\n");
 		log("\n");
 		log("The fsm_extract pass is conservative about the cells that belong to a finite\n");
 		log("state machine. This pass can be used to merge additional auxiliary gates into\n");
 		log("the finite state machine.\n");
 		log("\n");
+		log("By default, fsm_expand is still a bit conservative regarding merging larger\n");
+		log("word-wide cells. Call with -full to consider all cells for merging.\n");
+		log("\n");
 	}
 	virtual void execute(std::vector<std::string> args, RTLIL::Design *design)
 	{
+		bool full_mode = false;
+
 		log_header(design, "Executing FSM_EXPAND pass (merging auxiliary logic into FSMs).\n");
-		extra_args(args, 1, design);
+
+		size_t argidx;
+		for (argidx = 1; argidx < args.size(); argidx++) {
+			if (args[argidx] == "-full") {
+				full_mode = true;
+				continue;
+			}
+			break;
+		}
+		extra_args(args, argidx, design);
 
 		for (auto &mod_it : design->modules_) {
 			if (!design->selected(mod_it.second))
@@ -269,7 +279,7 @@ struct FsmExpandPass : public Pass {
 				if (cell_it.second->type == "$fsm" && design->selected(mod_it.second, cell_it.second))
 					fsm_cells.push_back(cell_it.second);
 			for (auto c : fsm_cells) {
-				FsmExpand fsm_expand(c, design, mod_it.second);
+				FsmExpand fsm_expand(c, design, mod_it.second, full_mode);
 				fsm_expand.execute();
 			}
 		}