diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index 3bc02de5..96b74023 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -172,7 +172,6 @@ object Cyc_string2number2_(void *data, object cont, int argc, object str, ...);
 int binstr2int(const char *str);
 int octstr2int(const char *str);
 object Cyc_string_append(void *data, object cont, int argc, object str1, ...);
-object Cyc_string_append2(void *data, object cont, int argc, object str1, object str2);
 object Cyc_string_length(void *data, object str);
 object Cyc_string_byte_length(void *data, object str);
 object Cyc_substring(void *data, object cont, object str, object start,
diff --git a/runtime.c b/runtime.c
index 86fb5d60..3784ad9c 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2245,36 +2245,6 @@ object Cyc_string_append(void *data, object cont, int _argc, object str1, ...)
   Cyc_string_append_va_list(data, _argc);
 }
 
-object Cyc_string_append2(void *data, object cont, int _argc, object str1, object str2)
-{
-    int i = 0, total_cp = 0, total_len = 1;
-    int len[2];
-    char *buffer, *bufferp, *str[2];
-
-    Cyc_check_str(data, str1);
-    Cyc_check_str(data, str2);
-
-    str[0] = ((string_type *)str1)->str;
-    len[0] = string_len((str1));
-    total_len += len[0];
-    total_cp += string_num_cp((str1));
-
-    str[1] = ((string_type *)str2)->str;
-    len[1] = string_len((str2));
-    total_len += len[1];
-    total_cp += string_num_cp((str2));
-
-    buffer = bufferp = alloca(sizeof(char) * total_len);
-    for (i = 0; i < 2; i++) {
-        memcpy(bufferp, str[i], len[i]);
-        bufferp += len[i];
-    }
-    *bufferp = '\0';
-    make_string(result, buffer);
-    string_num_cp((&result)) = total_cp;
-    _return_closcall1(data, cont, &result);
-}
-
 object Cyc_string_length(void *data, object str)
 {
   Cyc_check_str(data, str);