diff --git a/bootstrap.conf b/bootstrap.conf
index b51e08a..a3ae473 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -32,6 +32,7 @@ gnulib_modules="
 	langinfo
 	netinet_in
 	progname
+	quote
 	realloc-gnu
 	stat
 	stddef
diff --git a/src/dhcpd-pools.c b/src/dhcpd-pools.c
index 46447e3..d7f57f0 100644
--- a/src/dhcpd-pools.c
+++ b/src/dhcpd-pools.c
@@ -49,6 +49,7 @@
 #include "closeout.h"
 #include "error.h"
 #include "progname.h"
+#include "quote.h"
 #include "xalloc.h"
 
 #include "dhcpd-pools.h"
@@ -81,7 +82,7 @@ static int return_limit(const char c)
 	if ('0' <= c && c < '8')
 		return c - '0';
 	clean_up();
-	error(EXIT_FAILURE, 0, "return_limit: output mask '%s' is illegal", optarg);
+	error(EXIT_FAILURE, 0, "return_limit: output mask %s is illegal", quote(optarg));
 	return 0;
 }
 
@@ -241,7 +242,7 @@ int main(int argc, char **argv)
 			/* Print help */
 			usage(EXIT_SUCCESS);
 		default:
-			error(EXIT_FAILURE, 0, "Try `%s --help' for more information.",
+			error(EXIT_FAILURE, 0, "Try %s --help for more information.",
 			      program_name);
 		}
 	}
@@ -284,7 +285,7 @@ int main(int argc, char **argv)
 		break;
 	default:
 		clean_up();
-		error(EXIT_FAILURE, 0, "main: unknown output format '%c'", print_mac_addreses_tmp[0]);
+		error(EXIT_FAILURE, 0, "unknown output format: %s", quote(print_mac_addreses_tmp));
 	}
 	/* Do the job */
 	set_ipv_functions(IPvUNKNOWN);
diff --git a/src/other.c b/src/other.c
index a61c460..cd2cb3a 100644
--- a/src/other.c
+++ b/src/other.c
@@ -51,6 +51,7 @@
 
 #include "error.h"
 #include "progname.h"
+#include "quote.h"
 
 #include "dhcpd-pools.h"
 #include "defaults.h"
@@ -378,7 +379,7 @@ double strtod_or_err(const char *restrict str, const char *restrict errmesg)
 		goto err;
 	return num;
  err:
-	error(EXIT_FAILURE, errno, "%s: '%s'", errmesg, str);
+	error(EXIT_FAILURE, errno, "%s: %s", errmesg, quote(str));
 	return 0;
 }
 
diff --git a/src/sort.c b/src/sort.c
index 266362d..0bc9a5b 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -46,6 +46,7 @@
 
 #include "error.h"
 #include "progname.h"
+#include "quote.h"
 
 #include "dhcpd-pools.h"
 
@@ -236,8 +237,11 @@ comparer_t field_selector(char c)
 	case 'e':
 		return comp_tcperc;
 	default:
-		clean_up();
-		error(EXIT_FAILURE, 0, "field_selector: unknown sort order `%c'", c);
+		{
+			char str[2] = { c, '\0' };
+			clean_up();
+			error(EXIT_FAILURE, 0, "field_selector: unknown sort order: %s", quote(str));
+		}
 	}
 	return NULL;
 }