diff --git a/techlibs/ecp5/synth_ecp5.cc b/techlibs/ecp5/synth_ecp5.cc
index 3b0c2ea9e..9f409ca51 100644
--- a/techlibs/ecp5/synth_ecp5.cc
+++ b/techlibs/ecp5/synth_ecp5.cc
@@ -199,6 +199,9 @@ struct SynthEcp5Pass : public ScriptPass
 		if (!design->full_selection())
 			log_cmd_error("This command only operates on fully selected designs!\n");
 
+		if (abc9 && retime)
+				log_cmd_error("-retime option not currently compatible with -abc9!\n");
+
 		log_header(design, "Executing SYNTH_ECP5 pass.\n");
 		log_push();
 
diff --git a/techlibs/ice40/synth_ice40.cc b/techlibs/ice40/synth_ice40.cc
index 9dd5d81f7..2c75215cb 100644
--- a/techlibs/ice40/synth_ice40.cc
+++ b/techlibs/ice40/synth_ice40.cc
@@ -227,6 +227,9 @@ struct SynthIce40Pass : public ScriptPass
 		if (device_opt != "hx" && device_opt != "lp" && device_opt !="u")
 			log_cmd_error("Invalid or no device specified: '%s'\n", device_opt.c_str());
 
+		if (abc == "abc9" && retime)
+			log_cmd_error("-retime option not currently compatible with -abc9!\n");
+
 		log_header(design, "Executing SYNTH_ICE40 pass.\n");
 		log_push();
 
@@ -296,7 +299,7 @@ struct SynthIce40Pass : public ScriptPass
 				run("techmap");
 			else
 				run("techmap -map +/techmap.v -map +/ice40/arith_map.v");
-			if ((retime || help_mode) && abc != "abc9")
+			if (retime || help_mode)
 				run(abc + " -dff", "(only if -retime)");
 			run("ice40_opt");
 		}
diff --git a/techlibs/xilinx/synth_xilinx.cc b/techlibs/xilinx/synth_xilinx.cc
index b7c32d2e0..22c4a1a1b 100644
--- a/techlibs/xilinx/synth_xilinx.cc
+++ b/techlibs/xilinx/synth_xilinx.cc
@@ -25,8 +25,8 @@
 USING_YOSYS_NAMESPACE
 PRIVATE_NAMESPACE_BEGIN
 
-#define XC7_WIRE_DELAY "300" // Number with which ABC will map a 6-input gate
-                             // to one LUT6 (instead of a LUT5 + LUT2)
+#define XC7_WIRE_DELAY 300 // Number with which ABC will map a 6-input gate
+                           // to one LUT6 (instead of a LUT5 + LUT2)
 
 struct SynthXilinxPass : public ScriptPass
 {
@@ -195,11 +195,14 @@ struct SynthXilinxPass : public ScriptPass
 		extra_args(args, argidx, design);
 
 		if (family != "xcup" && family != "xcu" && family != "xc7" && family != "xc6s")
-			log_cmd_error("Invalid Xilinx -family setting: %s\n", family.c_str());
+			log_cmd_error("Invalid Xilinx -family setting: '%s'.\n", family.c_str());
 
 		if (!design->full_selection())
 			log_cmd_error("This command only operates on fully selected designs!\n");
 
+		if (abc9 && retime)
+			log_cmd_error("-retime option not currently compatible with -abc9!\n");
+
 		log_header(design, "Executing SYNTH_XILINX pass.\n");
 		log_push();
 
@@ -297,9 +300,9 @@ struct SynthXilinxPass : public ScriptPass
 				if (family != "xc7")
 					log_warning("'synth_xilinx -abc9' currently supports '-family xc7' only.\n");
 				if (nowidelut)
-					run("abc9 -lut +/xilinx/abc_xc7_nowide.lut -box +/xilinx/abc_xc7.box -W " + std::string(XC7_WIRE_DELAY) + string(retime ? " -dff" : ""));
+					run("abc9 -lut +/xilinx/abc_xc7_nowide.lut -box +/xilinx/abc_xc7.box -W " + std::to_string(XC7_WIRE_DELAY));
 				else
-					run("abc9 -lut +/xilinx/abc_xc7.lut -box +/xilinx/abc_xc7.box -W " + std::string(XC7_WIRE_DELAY) + string(retime ? " -dff" : ""));
+					run("abc9 -lut +/xilinx/abc_xc7.lut -box +/xilinx/abc_xc7.box -W " + std::to_string(XC7_WIRE_DELAY));
 			}
 			else {
 				if (nowidelut)