diff --git a/tc/q_fifo.c b/tc/q_fifo.c
index 6242a98..c9ab123 100644
--- a/tc/q_fifo.c
+++ b/tc/q_fifo.c
@@ -38,7 +38,7 @@
 		if (strcmp(*argv, "limit") == 0) {
 			NEXT_ARG();
 			if (get_size(&opt.limit, *argv)) {
-				fprintf(stderr, "Illegal \"limit\"\n");
+				fprintf(stderr, "%s: Illegal value for \"limit\": \"%s\"\n", qu->id, *argv);
 				return -1;
 			}
 			ok++;
@@ -46,7 +46,7 @@
 			explain();
 			return -1;
 		} else {
-			fprintf(stderr, "What is \"%s\"?\n", *argv);
+			fprintf(stderr, "%s: unknown parameter \"%s\"\n", qu->id, *argv);
 			explain();
 			return -1;
 		}
diff --git a/tc/q_tbf.c b/tc/q_tbf.c
index dc556fe..72cfff6 100644
--- a/tc/q_tbf.c
+++ b/tc/q_tbf.c
@@ -30,9 +30,9 @@
 	fprintf(stderr, "[ overhead BYTES ] [ linklayer TYPE ]\n");
 }
 
-static void explain1(char *arg)
+static void explain1(const char *arg, const char *val)
 {
-	fprintf(stderr, "Illegal \"%s\"\n", arg);
+	fprintf(stderr, "tbf: illegal value for \"%s\": \"%s\"\n", arg, val);
 }
 
 
@@ -53,130 +53,150 @@
 	while (argc > 0) {
 		if (matches(*argv, "limit") == 0) {
 			NEXT_ARG();
-			if (opt.limit || latency) {
-				fprintf(stderr, "Double \"limit/latency\" spec\n");
+			if (opt.limit) {
+				fprintf(stderr, "tbf: duplicate \"limit\" specification\n");
+				return -1;
+			}
+			if (latency) {
+				fprintf(stderr, "tbf: specifying both \"latency\" and \"limit\" is not allowed\n");
 				return -1;
 			}
 			if (get_size(&opt.limit, *argv)) {
-				explain1("limit");
+				explain1("limit", *argv);
 				return -1;
 			}
 			ok++;
 		} else if (matches(*argv, "latency") == 0) {
 			NEXT_ARG();
-			if (opt.limit || latency) {
-				fprintf(stderr, "Double \"limit/latency\" spec\n");
+			if (latency) {
+				fprintf(stderr, "tbf: duplicate \"latency\" specification\n");
+				return -1;
+			}
+			if (opt.limit) {
+				fprintf(stderr, "tbf: specifying both \"limit\" and \"/latency\" is not allowed\n");
 				return -1;
 			}
 			if (get_time(&latency, *argv)) {
-				explain1("latency");
+				explain1("latency", *argv);
 				return -1;
 			}
 			ok++;
 		} else if (matches(*argv, "burst") == 0 ||
 			strcmp(*argv, "buffer") == 0 ||
 			strcmp(*argv, "maxburst") == 0) {
+			const char *parm_name = *argv;
 			NEXT_ARG();
 			if (buffer) {
-				fprintf(stderr, "Double \"buffer/burst\" spec\n");
+				fprintf(stderr, "tbf: duplicate \"buffer/burst/maxburst\" specification\n");
 				return -1;
 			}
 			if (get_size_and_cell(&buffer, &Rcell_log, *argv) < 0) {
-				explain1("buffer");
+				explain1(parm_name, *argv);
 				return -1;
 			}
 			ok++;
 		} else if (strcmp(*argv, "mtu") == 0 ||
 			   strcmp(*argv, "minburst") == 0) {
+			const char *parm_name = *argv;
 			NEXT_ARG();
 			if (mtu) {
-				fprintf(stderr, "Double \"mtu/minburst\" spec\n");
+				fprintf(stderr, "tbf: duplicate \"mtu/minburst\" specification\n");
 				return -1;
 			}
 			if (get_size_and_cell(&mtu, &Pcell_log, *argv) < 0) {
-				explain1("mtu");
+				explain1(parm_name, *argv);
 				return -1;
 			}
 			ok++;
 		} else if (strcmp(*argv, "mpu") == 0) {
 			NEXT_ARG();
 			if (mpu) {
-				fprintf(stderr, "Double \"mpu\" spec\n");
+				fprintf(stderr, "tbf: duplicate \"mpu\" specification\n");
 				return -1;
 			}
 			if (get_size(&mpu, *argv)) {
-				explain1("mpu");
+				explain1("mpu", *argv);
 				return -1;
 			}
 			ok++;
 		} else if (strcmp(*argv, "rate") == 0) {
 			NEXT_ARG();
 			if (opt.rate.rate) {
-				fprintf(stderr, "Double \"rate\" spec\n");
+				fprintf(stderr, "tbf: duplicate \"rate\" specification\n");
 				return -1;
 			}
 			if (get_rate(&opt.rate.rate, *argv)) {
-				explain1("rate");
+				explain1("rate", *argv);
 				return -1;
 			}
 			ok++;
 		} else if (matches(*argv, "peakrate") == 0) {
 			NEXT_ARG();
 			if (opt.peakrate.rate) {
-				fprintf(stderr, "Double \"peakrate\" spec\n");
+				fprintf(stderr, "tbf: duplicate \"peakrate\" specification\n");
 				return -1;
 			}
 			if (get_rate(&opt.peakrate.rate, *argv)) {
-				explain1("peakrate");
+				explain1("peakrate", *argv);
 				return -1;
 			}
 			ok++;
 		} else if (matches(*argv, "overhead") == 0) {
 			NEXT_ARG();
 			if (overhead) {
-				fprintf(stderr, "Double \"overhead\" spec\n");
+				fprintf(stderr, "tbf: duplicate \"overhead\" specification\n");
 				return -1;
 			}
 			if (get_u16(&overhead, *argv, 10)) {
-				explain1("overhead"); return -1;
+				explain1("overhead", *argv); return -1;
 			}
 		} else if (matches(*argv, "linklayer") == 0) {
 			NEXT_ARG();
 			if (get_linklayer(&linklayer, *argv)) {
-				explain1("linklayer"); return -1;
+				explain1("linklayer", *argv); return -1;
 			}
 		} else if (strcmp(*argv, "help") == 0) {
 			explain();
 			return -1;
 		} else {
-			fprintf(stderr, "What is \"%s\"?\n", *argv);
+			fprintf(stderr, "tbf: unknown parameter \"%s\"\n", *argv);
 			explain();
 			return -1;
 		}
 		argc--; argv++;
 	}
 
-	if (!ok) {
-		explain();
-		return -1;
-	}
+        int verdict = 0;
 
-	if (opt.rate.rate == 0 || !buffer) {
-		fprintf(stderr, "Both \"rate\" and \"burst\" are required.\n");
-		return -1;
+        /* Be nice to the user: try to emit all error messages in
+         * one go rather than reveal one more problem when a
+         * previous one has been fixed.
+         */
+	if (opt.rate.rate == 0) {
+		fprintf(stderr, "tbf: the \"rate\" parameter is mandatory.\n");
+		verdict = -1;
+	}
+	if (!buffer) {
+		fprintf(stderr, "tbf: the \"burst\" parameter is mandatory.\n");
+		verdict = -1;
 	}
 	if (opt.peakrate.rate) {
 		if (!mtu) {
-			fprintf(stderr, "\"mtu\" is required, if \"peakrate\" is requested.\n");
-			return -1;
+			fprintf(stderr, "tbf: when \"peakrate\" is specified, \"mtu\" must also be specified.\n");
+			verdict = -1;
 		}
 	}
 
 	if (opt.limit == 0 && latency == 0) {
-		fprintf(stderr, "Either \"limit\" or \"latency\" are required.\n");
-		return -1;
+		fprintf(stderr, "tbf: either \"limit\" or \"latency\" is required.\n");
+		verdict = -1;
 	}
 
+        if (verdict != 0) {
+                explain();
+                return verdict;
+        }
+
 	if (opt.limit == 0) {
 		double lim = opt.rate.rate*(double)latency/TIME_UNITS_PER_SEC + buffer;
 		if (opt.peakrate.rate) {
@@ -190,7 +210,7 @@
 	opt.rate.mpu      = mpu;
 	opt.rate.overhead = overhead;
 	if (tc_calc_rtable(&opt.rate, rtab, Rcell_log, mtu, linklayer) < 0) {
-		fprintf(stderr, "TBF: failed to calculate rate table.\n");
+		fprintf(stderr, "tbf: failed to calculate rate table.\n");
 		return -1;
 	}
 	opt.buffer = tc_calc_xmittime(opt.rate.rate, buffer);
@@ -199,7 +219,7 @@
 		opt.peakrate.mpu      = mpu;
 		opt.peakrate.overhead = overhead;
 		if (tc_calc_rtable(&opt.peakrate, ptab, Pcell_log, mtu, linklayer) < 0) {
-			fprintf(stderr, "TBF: failed to calculate peak rate table.\n");
+			fprintf(stderr, "tbf: failed to calculate peak rate table.\n");
 			return -1;
 		}
 		opt.mtu = tc_calc_xmittime(opt.peakrate.rate, mtu);