diff --git a/lib/access.c b/lib/access.c
index 50f7f230..a784579b 100644
--- a/lib/access.c
+++ b/lib/access.c
@@ -92,15 +92,11 @@ sensors_for_all_config_chips(const sensors_chip_name *name,
 const sensors_chip_feature *sensors_lookup_feature_nr(const sensors_chip_name *chip,
 						      int feature)
 {
-	int i, j;
-	const sensors_chip_feature *features;
+	int i;
 
 	for (i = 0; i < sensors_proc_chips_count; i++)
 		if (sensors_match_chip(&sensors_proc_chips[i].chip, chip)) {
-			features = sensors_proc_chips[i].feature;
-			for (j = 0; features[j].data.name; j++)
-				if (features[j].data.number == feature)
-					return features + j;
+			return sensors_proc_chips[i].feature + feature;
 		}
 	return NULL;
 }
diff --git a/lib/sysfs.c b/lib/sysfs.c
index 3fdd9e53..5438de7d 100644
--- a/lib/sysfs.c
+++ b/lib/sysfs.c
@@ -178,6 +178,21 @@ static int sensors_read_dynamic_chip(sensors_chip_features *chip,
 		}
 	}
 
+	/* Renumber the features linearly, so that feature number N is at
+	   position N in the array. This allows for O(1) look-ups. */
+	for (i = 0; i < fnum; i++) {
+		int j, old;
+
+		old = dyn_features[i].data.number;
+		dyn_features[i].data.number = i;
+		for (j = i + 1;
+		     j < fnum && dyn_features[j].data.mapping != SENSORS_NO_MAPPING;
+		     j++) {
+			if (dyn_features[j].data.mapping == old)
+				dyn_features[j].data.mapping = i;
+		}
+	}
+
 	chip->feature = dyn_features;
 
 exit_free: