diff --git a/src/features.c b/src/features.c
index 782a5996..0036ad27 100644
--- a/src/features.c
+++ b/src/features.c
@@ -26,13 +26,20 @@ void feature_array_add_printf(cstring_array *features, char *format, ...) {
 }
 
 
-bool feature_counts_update_or_add(khash_t(str_double) *features, char *feature, double count, bool add) {
+bool feature_counts_update_or_add(khash_t(str_double) *features, char *feature, double count, bool copy, bool add) {
     khiter_t k;
 
-    k = kh_get(str_double, features, feature);
+    char *str;
+    if (copy) {
+        str = strdup(feature);
+    } else {
+        str = feature;
+    }
+
+    k = kh_get(str_double, features, str);
     if (k == kh_end(features)) {
         int ret;
-        k = kh_put(str_double, features, feature, &ret);
+        k = kh_put(str_double, features, str, &ret);
         if (ret < 0) return false;
 
         kh_value(features, k) = count;
@@ -46,9 +53,17 @@ bool feature_counts_update_or_add(khash_t(str_double) *features, char *feature,
 
 
 inline bool feature_counts_add(khash_t(str_double) *features, char *feature, double count) {
-    return feature_counts_update_or_add(features, feature, count, true);
+    return feature_counts_update_or_add(features, feature, count, true, true);
+}
+
+inline bool feature_counts_add_no_copy(khash_t(str_double) *features, char *feature, double count) {
+    return feature_counts_update_or_add(features, feature, count, false, true);
 }
 
 inline bool feature_counts_update(khash_t(str_double) *features, char *feature, double count) {
-    return feature_counts_update_or_add(features, feature, count, false);
+    return feature_counts_update_or_add(features, feature, count, true, false);
+}
+
+inline bool feature_counts_update_no_copy(khash_t(str_double) *features, char *feature, double count) {
+    return feature_counts_update_or_add(features, feature, count, false, false);
 }
diff --git a/src/features.h b/src/features.h
index 97fbb3ec..6f99ae3e 100644
--- a/src/features.h
+++ b/src/features.h
@@ -18,7 +18,9 @@ void feature_array_add_printf(cstring_array *features, char *format, ...);
 // Add feature count to dictionary
 
 bool feature_counts_add(khash_t(str_double) *features, char *feature, double count); 
+bool feature_counts_add_no_copy(khash_t(str_double) *features, char *feature, double count);
 bool feature_counts_update(khash_t(str_double) *features, char *feature, double count); 
+bool feature_counts_update_no_copy(khash_t(str_double) *features, char *feature, double count); 
 
 VECTOR_INIT(feature_count_array, khash_t(str_double) *)