diff --git a/runtime.c b/runtime.c
index ef2bafb0..c75c8ae1 100644
--- a/runtime.c
+++ b/runtime.c
@@ -2032,7 +2032,7 @@ object Cyc_string_cmp(void *data, object str1, object str2)
 }
 
 #define Cyc_string_append_va_list(data, argc) { \
-    int i = 0, total_len = 1; \
+    int i = 0, total_cp = 0, total_len = 1; \
     int *len = alloca(sizeof(int) * argc); \
     char *buffer, *bufferp, **str = alloca(sizeof(char *) * argc); \
     object tmp; \
@@ -2041,6 +2041,7 @@ object Cyc_string_cmp(void *data, object str1, object str2)
       str[i] = ((string_type *)str1)->str; \
       len[i] = string_len((str1)); \
       total_len += len[i]; \
+      total_cp += string_num_cp(str1); \
     } \
     for (i = 1; i < argc; i++) { \
       tmp = va_arg(ap, object); \
@@ -2048,6 +2049,7 @@ object Cyc_string_cmp(void *data, object str1, object str2)
       str[i] = ((string_type *)tmp)->str; \
       len[i] = string_len((tmp)); \
       total_len += len[i]; \
+      total_cp += string_num_cp(tmp); \
     } \
     buffer = bufferp = alloca(sizeof(char) * total_len); \
     for (i = 0; i < argc; i++) { \
@@ -2056,6 +2058,7 @@ object Cyc_string_cmp(void *data, object str1, object str2)
     } \
     *bufferp = '\0'; \
     make_string(result, buffer); \
+    string_num_cp(result) = total_cp; \
     va_end(ap); \
     _return_closcall1(data, cont, &result); \
 }
@@ -2078,7 +2081,7 @@ object Cyc_string_append(void *data, object cont, int _argc, object str1, ...)
 object Cyc_string_length(void *data, object str)
 {
   Cyc_check_str(data, str);
-  return obj_int2obj(string_len(str));
+  return obj_int2obj(string_num_cp(str));
 }
 
 object Cyc_string_set(void *data, object str, object k, object chr)