diff --git a/CHANGELOG b/CHANGELOG
index ae7d28236..646d63a63 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -12,6 +12,7 @@ Yosys 0.9 .. Yosys 0.9-dev
     - Added "synth_xilinx -abc9" (experimental)
     - Added "synth_ice40 -abc9" (experimental)
     - Added "synth -abc9" (experimental)
+    - Added "synth -keepdc"
     - Added "script -scriptwire
 
 
diff --git a/passes/opt/wreduce.cc b/passes/opt/wreduce.cc
index 1fbc41082..f749c8249 100644
--- a/passes/opt/wreduce.cc
+++ b/passes/opt/wreduce.cc
@@ -497,7 +497,7 @@ struct WreducePass : public Pass {
 		log("        flows that use the 'memory_memx' pass.\n");
 		log("\n");
 		log("    -keepdc\n");
-		log("        Do not optimize explicit don't-care values.\n");
+		log("        Do not optimize explicit don't-care values on $mux cells.\n");
 		log("\n");
 	}
 	void execute(std::vector<std::string> args, Design *design) YS_OVERRIDE
diff --git a/techlibs/common/synth.cc b/techlibs/common/synth.cc
index 555de9fba..af70cc498 100644
--- a/techlibs/common/synth.cc
+++ b/techlibs/common/synth.cc
@@ -78,6 +78,9 @@ struct SynthPass : public ScriptPass
 		log("    -abc9\n");
 		log("        use new ABC9 flow (EXPERIMENTAL)\n");
 		log("\n");
+		log("    -keepdc\n");
+		log("        do not optimize explicit don't-care values on $mux cells.\n");
+		log("\n");
 		log("\n");
 		log("The following commands are executed by this synthesis command:\n");
 		help_script();
@@ -85,7 +88,7 @@ struct SynthPass : public ScriptPass
 	}
 
 	string top_module, fsm_opts, memory_opts, abc;
-	bool autotop, flatten, noalumacc, nofsm, noabc, noshare;
+	bool autotop, flatten, noalumacc, nofsm, noabc, noshare, keepdc;
 	int lut;
 
 	void clear_flags() YS_OVERRIDE
@@ -102,6 +105,7 @@ struct SynthPass : public ScriptPass
 		noabc = false;
 		noshare = false;
 		abc = "abc";
+		keepdc = false;
 	}
 
 	void execute(std::vector<std::string> args, RTLIL::Design *design) YS_OVERRIDE
@@ -167,6 +171,10 @@ struct SynthPass : public ScriptPass
 				abc = "abc9";
 				continue;
 			}
+			if (args[argidx] == "-keepdc") {
+				keepdc = true;
+				continue;
+			}
 			break;
 		}
 		extra_args(args, argidx, design);
@@ -211,7 +219,10 @@ struct SynthPass : public ScriptPass
 			run("opt_clean");
 			run("check");
 			run("opt");
-			run("wreduce");
+			if (help_mode)
+				run("wreduce [-keepdc]");
+			else
+				run("wreduce" + std::string(keepdc ? " -keepdc" : ""));
 			run("peepopt");
 			run("opt_clean");
 			if (help_mode)