Index: src/stream.c
==================================================================
--- src/stream.c
+++ src/stream.c
@@ -118,11 +118,11 @@
 					free(ret_str);
 					return NULL;
 				}
 				cfw_string_set_nocopy(ret, ret_str, ret_len);
 
-				if (stream->cache_len - i - 1 > 0) {
+				if (stream->cache_len > i + 1) {
 					if ((new_cache = malloc(
 					    stream->cache_len - i - 1)) == NULL)
 						return NULL;
 					memcpy(new_cache, stream->cache + i + 1,
 					    stream->cache_len - i - 1);
@@ -205,11 +205,11 @@
 					free(ret_str);
 					return NULL;
 				}
 				cfw_string_set_nocopy(ret, ret_str, ret_len);
 
-				if (buf_len - i - 1 > 0) {
+				if (buf_len > i + 1) {
 					new_cache = malloc(buf_len - i - 1);
 					if (new_cache == NULL) {
 						free(buf);
 						return NULL;
 					}

Index: src/string.c
==================================================================
--- src/string.c
+++ src/string.c
@@ -217,10 +217,13 @@
 
 bool
 cfw_string_append(CFWString *str, CFWString *append)
 {
 	char *new;
+
+	if (append == NULL)
+		return true;
 
 	if ((new = realloc(str->data, str->len + append->len + 1)) == NULL)
 		return false;
 
 	memcpy(new + str->len, append->data, append->len);
@@ -233,12 +236,17 @@
 }
 
 bool
 cfw_string_append_c(CFWString *str, const char *append)
 {
-	size_t append_len = strlen(append);
 	char *new;
+	size_t append_len;
+
+	if (append == NULL)
+		return true;
+
+	append_len = strlen(append);
 
 	if ((new = realloc(str->data, str->len + append_len + 1)) == NULL)
 		return false;
 
 	memcpy(new + str->len, append, append_len);