diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 95a24c93f..a09f4a0d1 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -3437,7 +3437,7 @@ void RTLIL::SigSpec::extend_u0(int width, bool is_signed)
 
 	if (width_ < width) {
 		RTLIL::SigBit padding = width_ > 0 ? (*this)[width_ - 1] : RTLIL::State::Sx;
-		if (padding != RTLIL::State::Sx && !is_signed)
+		if (!is_signed)
 			padding = RTLIL::State::S0;
 		while (width_ < width)
 			append(padding);