diff --git a/sys/include/net/nanocoap.h b/sys/include/net/nanocoap.h
index a6612fd918..5dbc5e28be 100644
--- a/sys/include/net/nanocoap.h
+++ b/sys/include/net/nanocoap.h
@@ -1046,6 +1046,27 @@ static inline ssize_t coap_opt_add_uri_query(coap_pkt_t *pkt, const char *key,
  */
 ssize_t coap_opt_add_proxy_uri(coap_pkt_t *pkt, const char *uri);
 
+/**
+ * @brief   Encode the given array of characters as option(s) into pkt
+ *
+ * Use separator to split array of characters into multiple options.
+ *
+ * @post pkt.payload advanced to first byte after option(s)
+ * @post pkt.payload_len reduced by option(s) length
+ *
+ * @param[in,out] pkt         pkt referencing target buffer
+ * @param[in]     optnum      option number to use
+ * @param[in]     chars       array of characters to encode as option
+ * @param[in]     chars_len   length of @p chars
+ * @param[in]     separator   character used in @p string to separate parts
+ *
+ * @return        number of bytes written to buffer
+ * @return        <0 on error
+ * @return        -ENOSPC if no available options or insufficient buffer space
+ */
+ssize_t coap_opt_add_chars(coap_pkt_t *pkt, uint16_t optnum, const char *chars,
+                           size_t chars_len, char separator);
+
 /**
  * @brief   Encode the given string as option(s) into pkt
  *
@@ -1063,7 +1084,11 @@ ssize_t coap_opt_add_proxy_uri(coap_pkt_t *pkt, const char *uri);
  * @return        <0 on error
  * @return        -ENOSPC if no available options or insufficient buffer space
  */
-ssize_t coap_opt_add_string(coap_pkt_t *pkt, uint16_t optnum, const char *string, char separator);
+static inline ssize_t coap_opt_add_string(coap_pkt_t *pkt, uint16_t optnum,
+                                          const char *string, char separator)
+{
+    return coap_opt_add_chars(pkt, optnum, string, strlen(string), separator);
+}
 
 /**
  * @brief   Adds one or multiple Uri-Path options in the form '/path' into pkt
diff --git a/sys/net/application_layer/nanocoap/nanocoap.c b/sys/net/application_layer/nanocoap/nanocoap.c
index 4611e10973..580899c219 100644
--- a/sys/net/application_layer/nanocoap/nanocoap.c
+++ b/sys/net/application_layer/nanocoap/nanocoap.c
@@ -819,28 +819,31 @@ static ssize_t _add_opt_pkt(coap_pkt_t *pkt, uint16_t optnum, const uint8_t *val
     return optlen;
 }
 
-ssize_t coap_opt_add_string(coap_pkt_t *pkt, uint16_t optnum, const char *string,
-                           char separator)
+ssize_t coap_opt_add_chars(coap_pkt_t *pkt, uint16_t optnum, const char *chars,
+                           size_t chars_len, char separator)
 {
-    size_t unread_len = strlen(string);
-    if (!unread_len) {
+    /* chars_len denotes the length of the chars buffer and is
+     * gradually decremented below while iterating over the buffer */
+    if (!chars_len) {
         return 0;
     }
-    char *uripos = (char *)string;
+
+    char *uripos = (char *)chars;
+    char *endpos = ((char *)chars + chars_len);
     size_t write_len = 0;
 
-    while (unread_len) {
+    while (chars_len) {
         size_t part_len;
         if (*uripos == separator) {
             uripos++;
         }
         uint8_t *part_start = (uint8_t *)uripos;
 
-        while (unread_len) {
+        while (chars_len) {
             /* must decrement separately from while loop test to ensure
              * the value remains non-negative */
-            unread_len--;
-            if ((*uripos == separator) || (*uripos == '\0')) {
+            chars_len--;
+            if ((*uripos == separator) || (uripos == endpos)) {
                 break;
             }
             uripos++;
diff --git a/tests/unittests/tests-nanocoap/tests-nanocoap.c b/tests/unittests/tests-nanocoap/tests-nanocoap.c
index 8f564e4510..52146f1ab2 100644
--- a/tests/unittests/tests-nanocoap/tests-nanocoap.c
+++ b/tests/unittests/tests-nanocoap/tests-nanocoap.c
@@ -745,6 +745,35 @@ static void test_nanocoap__empty(void)
     TEST_ASSERT_EQUAL_INT(-EBADMSG, res);
 }
 
+/*
+ * Test adding a path from an unterminated string
+ */
+static void test_nanocoap__add_path_unterminated_string(void)
+{
+    uint8_t buf[_BUF_SIZE];
+    coap_pkt_t pkt;
+    uint16_t msgid = 0xABCD;
+    uint8_t token[2] = {0xDA, 0xEC};
+    char path[16] = "/time";
+    size_t path_len = strlen("/time");
+
+    /* some random non-zero character at the end of /time */
+    path[path_len] = 'Z';
+
+    size_t len = coap_build_hdr((coap_hdr_t *)&buf[0], COAP_TYPE_NON,
+                                &token[0], 2, COAP_METHOD_GET, msgid);
+
+    coap_pkt_init(&pkt, &buf[0], sizeof(buf), len);
+    coap_opt_add_chars(&pkt, COAP_OPT_URI_PATH, &path[0], path_len, '/');
+
+    char uri[10] = {0};
+    ssize_t parsed_path_len = coap_get_uri_path(&pkt, (uint8_t *)&uri[0]);
+
+    /* we subtract one byte for '\0' at the end from parsed_uri_path */
+    TEST_ASSERT_EQUAL_INT(path_len, parsed_path_len - 1);
+    TEST_ASSERT_EQUAL_INT(0, strncmp(path, uri, path_len));
+}
+
 Test *tests_nanocoap_tests(void)
 {
     EMB_UNIT_TESTFIXTURES(fixtures) {
@@ -769,6 +798,7 @@ Test *tests_nanocoap_tests(void)
         new_TestFixture(test_nanocoap__server_option_count_overflow_check),
         new_TestFixture(test_nanocoap__server_option_count_overflow),
         new_TestFixture(test_nanocoap__empty),
+        new_TestFixture(test_nanocoap__add_path_unterminated_string),
     };
 
     EMB_UNIT_TESTCALLER(nanocoap_tests, NULL, NULL, fixtures);