diff --git a/cmdline/stress.c b/cmdline/stress.c
index 8e15d543..6a7b517c 100644
--- a/cmdline/stress.c
+++ b/cmdline/stress.c
@@ -619,6 +619,9 @@ void stress_functions(dc_context_t* context)
 		assert( !DC_EVENT_RETURNS_STRING(100) );
 		assert( !DC_EVENT_RETURNS_STRING(300) );
 		assert( !DC_EVENT_RETURNS_STRING(400) );
+
+		assert( dc_utf8_strlen("c")==1 && strlen("c")==1 );
+		assert( dc_utf8_strlen("ä")==1 && strlen("ä")==2 );
 	}
 
 	/* test dc_array_t
diff --git a/src/dc_tools.c b/src/dc_tools.c
index bef83f1a..9abe1222 100644
--- a/src/dc_tools.c
+++ b/src/dc_tools.c
@@ -420,9 +420,12 @@ error:
 }
 
 
-#if 0 /* not needed at the moment */
-static size_t dc_utf8_strlen(const char* s)
+size_t dc_utf8_strlen(const char* s)
 {
+	if (s==NULL) {
+		return 0;
+	}
+
 	size_t i = 0;
 	size_t j = 0;
 	while (s[i]) {
@@ -432,11 +435,14 @@ static size_t dc_utf8_strlen(const char* s)
 	}
 	return j;
 }
-#endif
 
 
 static size_t dc_utf8_strnlen(const char* s, size_t n)
 {
+	if (s==NULL) {
+		return 0;
+	}
+
 	size_t i = 0;
 	size_t j = 0;
 	while (i < n) {
diff --git a/src/dc_tools.h b/src/dc_tools.h
index 213647f6..4a7d5750 100644
--- a/src/dc_tools.h
+++ b/src/dc_tools.h
@@ -41,6 +41,7 @@ char*   dc_binary_to_uc_hex        (const uint8_t* buf, size_t bytes);
 void    dc_remove_cr_chars         (char*); /* remove all \r characters from string */
 void    dc_unify_lineends          (char*);
 void    dc_replace_bad_utf8_chars  (char*); /* replace bad UTF-8 characters by sequences of `_` (to avoid problems in filenames, we do not use eg. `?`) the function is useful if strings are unexpectingly encoded eg. as ISO-8859-1 */
+size_t  dc_utf8_strlen             (const char*);
 void    dc_truncate_str            (char*, int approx_characters);
 void    dc_truncate_n_unwrap_str   (char*, int approx_characters, int do_unwrap);
 carray* dc_split_into_lines        (const char* buf_terminated); /* split string into lines*/