diff --git a/usr.bin/units/units.c b/usr.bin/units/units.c
index b222ade449df..88363e2e6c34 100644
--- a/usr.bin/units/units.c
+++ b/usr.bin/units/units.c
@@ -763,11 +763,9 @@ main(int argc, char **argv)
 	EditLine *el;
 	HistEvent ev;
 	int inputsz;
-	char const * history_file;
 
 	quiet = false;
 	readfile = false;
-	history_file = NULL;
 	outputformat = numfmt;
 	quit = false;
 	while ((optchar = getopt_long(argc, argv, "+ehf:o:qtvH:UV", longopts, NULL)) != -1) {
@@ -783,7 +781,7 @@ main(int argc, char **argv)
 				readunits(optarg);
 			break;
 		case 'H':
-			history_file = optarg;
+			/* Ignored, for compatibility with GNU units. */
 			break;
 		case 'q':
 			quiet = true;