diff --git a/llama.cpp b/llama.cpp
index b6e2ade91..a11bf78dc 100644
--- a/llama.cpp
+++ b/llama.cpp
@@ -11951,6 +11951,7 @@ static std::vector<llama_grammar_candidate> llama_grammar_reject_candidates_for_
         const std::vector<llama_grammar_candidate>            & candidates) {
 
     std::vector<llama_grammar_candidate> rejects;
+    rejects.reserve(candidates.size());
 
     if (stack.empty()) {
         for (const auto & tok : candidates) {
@@ -11964,6 +11965,8 @@ static std::vector<llama_grammar_candidate> llama_grammar_reject_candidates_for_
     const llama_grammar_element * stack_pos = stack.back();
 
     std::vector<llama_grammar_candidate> next_candidates;
+    next_candidates.reserve(candidates.size());
+
     for (const auto & tok : candidates) {
         if (*tok.code_points == 0) {
             // reached end of full codepoints in token, reject iff it ended in a partial sequence