diff --git a/Python/ast.c b/Python/ast.c
index 3c339f0..30275a6 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -191,6 +191,10 @@
 
     if (flags && flags->cf_flags & PyCF_SOURCE_IS_UTF8) {
         c.c_encoding = "utf-8";
+        if (TYPE(n) == encoding_decl) {
+                ast_error(n, "encoding declaration in Unicode string");
+                goto error;
+        }
     } else if (TYPE(n) == encoding_decl) {
         c.c_encoding = STR(n);
         n = CHILD(n, 0);