diff --git a/passes/pmgen/ice40_dsp.pmg b/passes/pmgen/ice40_dsp.pmg
index 9330dd09b..6b6d2b56f 100644
--- a/passes/pmgen/ice40_dsp.pmg
+++ b/passes/pmgen/ice40_dsp.pmg
@@ -333,6 +333,9 @@ code
 			reject;
 		if (c.wire->get_bool_attribute(\keep))
 			reject;
+		Const init = c.wire->attributes.at(\init, State::Sx);
+		if (!init.is_fully_undef() && !init.is_fully_zero())
+			reject;
 	}
 endcode
 
diff --git a/passes/pmgen/xilinx_dsp.pmg b/passes/pmgen/xilinx_dsp.pmg
index e256f7d7e..0a345e88d 100644
--- a/passes/pmgen/xilinx_dsp.pmg
+++ b/passes/pmgen/xilinx_dsp.pmg
@@ -355,6 +355,9 @@ code
 			reject;
 		if (c.wire->get_bool_attribute(\keep))
 			reject;
+		Const init = c.wire->attributes.at(\init, State::Sx);
+		if (!init.is_fully_undef() && !init.is_fully_zero())
+			reject;
 	}
 endcode