diff --git a/src/core/ngx_parse.c b/src/core/ngx_parse.c
index 7b60c5fb6..d35e60fac 100644
--- a/src/core/ngx_parse.c
+++ b/src/core/ngx_parse.c
@@ -17,6 +17,11 @@ ngx_parse_size(ngx_str_t *line)
     ssize_t  size, scale, max;
 
     len = line->len;
+
+    if (len == 0) {
+        return NGX_ERROR;
+    }
+
     unit = line->data[len - 1];
 
     switch (unit) {
@@ -58,6 +63,11 @@ ngx_parse_offset(ngx_str_t *line)
     size_t  len;
 
     len = line->len;
+
+    if (len == 0) {
+        return NGX_ERROR;
+    }
+
     unit = line->data[len - 1];
 
     switch (unit) {