diff --git a/techlibs/ice40/abc_hx.box b/techlibs/ice40/abc_hx.box
index c0ea742e2..3ea70bc91 100644
--- a/techlibs/ice40/abc_hx.box
+++ b/techlibs/ice40/abc_hx.box
@@ -3,11 +3,11 @@
 # NB: Inputs/Outputs must be ordered alphabetically
 #     (with exceptions for carry in/out)
 
-# Inputs: A B CI
+# Inputs: A B I0 I3 CI
 # Outputs: O CO
 #   (NB: carry chain input/output must be last
 #        input/output and have been moved there
 #        overriding the alphabetical ordering)
-$__ICE40_FULL_ADDER 1 1 3 2
-400 379 316
-259 231 126
+$__ICE40_CARRY_WRAPPER 1 1 5 2
+400 379 449 316 316
+259 231 -   -   126
diff --git a/techlibs/ice40/abc_lp.box b/techlibs/ice40/abc_lp.box
index d73b6d649..473e92fe9 100644
--- a/techlibs/ice40/abc_lp.box
+++ b/techlibs/ice40/abc_lp.box
@@ -3,11 +3,11 @@
 # NB: Inputs/Outputs must be ordered alphabetically
 #     (with exceptions for carry in/out)
 
-# Inputs: A B CI
+# Inputs: A B I0 I3 CI
 # Outputs: O CO
 #   (NB: carry chain input/output must be last
 #        input/output and have been moved there
 #        overriding the alphabetical ordering)
-$__ICE40_FULL_ADDER 1 1 3 2
-589 558 465
-675 609 186 
+$__ICE40_CARRY_WRAPPER 1 1 5 2
+589 558 661 465 465
+675 609 -   -   186
diff --git a/techlibs/ice40/abc_u.box b/techlibs/ice40/abc_u.box
index 42d666051..f00e247b8 100644
--- a/techlibs/ice40/abc_u.box
+++ b/techlibs/ice40/abc_u.box
@@ -3,11 +3,11 @@
 # NB: Inputs/Outputs must be ordered alphabetically
 #     (with exceptions for carry in/out)
 
-# Inputs: A B CI
+# Inputs: A B I0 I3 CI
 # Outputs: O CO
 #   (NB: carry chain input/output must be last
 #        input/output and have been moved there
 #        overriding the alphabetical ordering)
-$__ICE40_FULL_ADDER 1 1 3 2
-1231 1205 874
-675  609  278
+$__ICE40_CARRY_WRAPPER 1 1 5 2
+1231 1205 1285 874 874
+675  609  -    -   278
diff --git a/techlibs/ice40/cells_sim.v b/techlibs/ice40/cells_sim.v
index c7f3bdad2..2a7487f6b 100644
--- a/techlibs/ice40/cells_sim.v
+++ b/techlibs/ice40/cells_sim.v
@@ -142,15 +142,16 @@ module SB_CARRY (output CO, input I0, I1, CI);
 endmodule
 
 (* abc_box_id = 1, lib_whitebox *)
-module \$__ICE40_FULL_ADDER (
+module \$__ICE40_CARRY_WRAPPER (
 	(* abc_carry *)
 	output CO,
 	output O,
-	input A,
-	input B,
+	input A, B,
 	(* abc_carry *)
-	input CI
+	input CI,
+	input I0, I3
 );
+	parameter LUT = 0;
 	SB_CARRY carry (
 		.I0(A),
 		.I1(B),
@@ -158,16 +159,12 @@ module \$__ICE40_FULL_ADDER (
 		.CO(CO)
 	);
 	SB_LUT4 #(
-		//         I0: 1010 1010 1010 1010
-		//         I1: 1100 1100 1100 1100
-		//         I2: 1111 0000 1111 0000
-		//         I3: 1111 1111 0000 0000
-		.LUT_INIT(16'b 0110_1001_1001_0110)
+		.LUT_INIT(LUT)
 	) adder (
-		.I0(1'b0),
+		.I0(I0),
 		.I1(A),
 		.I2(B),
-		.I3(CI),
+		.I3(I3),
 		.O(O)
 	);
 endmodule
diff --git a/techlibs/ice40/ice40_opt.cc b/techlibs/ice40/ice40_opt.cc
index d5106b805..ea56d3f4d 100644
--- a/techlibs/ice40/ice40_opt.cc
+++ b/techlibs/ice40/ice40_opt.cc
@@ -84,7 +84,7 @@ static void run_ice40_opts(Module *module)
 			continue;
 		}
 
-		if (cell->type == "$__ICE40_FULL_ADDER")
+		if (cell->type == "$__ICE40_CARRY_WRAPPER")
 		{
 			SigSpec non_const_inputs, replacement_output;
 			int count_zeros = 0, count_ones = 0;
@@ -114,16 +114,17 @@ static void run_ice40_opts(Module *module)
 				optimized_co.insert(sigmap(cell->getPort("\\CO")[0]));
 				module->connect(cell->getPort("\\CO")[0], replacement_output);
 				module->design->scratchpad_set_bool("opt.did_something", true);
-				log("Optimized $__ICE40_FULL_ADDER cell back to logic (without SB_CARRY) %s.%s: CO=%s\n",
+				log("Optimized $__ICE40_CARRY_WRAPPER cell back to logic (without SB_CARRY) %s.%s: CO=%s\n",
 						log_id(module), log_id(cell), log_signal(replacement_output));
 				cell->type = "$lut";
-				cell->setPort("\\A", { State::S0, inbit[0], inbit[1], inbit[2] });
+				cell->setPort("\\A", { cell->getPort("\\I0"), inbit[0], inbit[1], cell->getPort("\\I3") });
 				cell->setPort("\\Y", cell->getPort("\\O"));
 				cell->unsetPort("\\B");
 				cell->unsetPort("\\CI");
+				cell->unsetPort("\\I0");
+				cell->unsetPort("\\I3");
 				cell->unsetPort("\\CO");
 				cell->unsetPort("\\O");
-				cell->setParam("\\LUT", RTLIL::Const::from_string("0110100110010110"));
 				cell->setParam("\\WIDTH", 4);
 			}
 			continue;
diff --git a/tests/ice40/ice40_opt.ys b/tests/ice40/ice40_opt.ys
new file mode 100644
index 000000000..b17c69c91
--- /dev/null
+++ b/tests/ice40/ice40_opt.ys
@@ -0,0 +1,26 @@
+read_verilog -icells -formal <<EOT
+module top(input CI, I0, output [1:0] CO, output O);
+    wire A = 1'b0, B = 1'b0;
+	\$__ICE40_CARRY_WRAPPER #(
+		//    A[0]: 1010 1010 1010 1010
+		//    A[1]: 1100 1100 1100 1100
+		//    A[2]: 1111 0000 1111 0000
+		//    A[3]: 1111 1111 0000 0000
+		.LUT(~16'b 0110_1001_1001_0110)
+	) u0 (
+		.A(A),
+		.B(B),
+		.CI(CI),
+		.I0(I0),
+		.I3(CI),
+		.CO(CO[0]),
+		.O(O)
+	);
+    SB_CARRY u1 (.I0(~A), .I1(~B), .CI(CI), .CO(CO[1]));
+endmodule
+EOT
+
+equiv_opt -assert -map +/ice40/cells_map.v -map +/ice40/cells_sim.v ice40_opt
+design -load postopt
+select -assert-count 1 t:*
+select -assert-count 1 t:$lut