diff --git a/c/enc/backward_references_hq.c b/c/enc/backward_references_hq.c
index 6325032e1..9415fab06 100644
--- a/c/enc/backward_references_hq.c
+++ b/c/enc/backward_references_hq.c
@@ -435,6 +435,8 @@ static size_t UpdateNodes(
   const CompoundDictionary* addon = &params->dictionary.compound;
   size_t gap = addon->total_size;
 
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ringbuffer_mask);
+
   EvaluateNode(block_start + stream_offset, pos, max_backward_limit, gap,
       starting_dist_cache, model, queue, nodes);
 
diff --git a/c/enc/hash.h b/c/enc/hash.h
index ba9b0d820..9533b05be 100644
--- a/c/enc/hash.h
+++ b/c/enc/hash.h
@@ -548,6 +548,8 @@ static BROTLI_INLINE void FindCompoundDictionaryMatch(
     source = (const uint8_t*)BROTLI_UNALIGNED_LOAD_PTR((const uint8_t**)tail);
   }
 
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+
   for (i = 0; i < 4; ++i) {
     const size_t distance = (size_t)distance_cache[i];
     size_t offset;
@@ -657,6 +659,8 @@ static BROTLI_INLINE size_t FindAllCompoundDictionaryMatches(
     source = (const uint8_t*)BROTLI_UNALIGNED_LOAD_PTR((const uint8_t**)tail);
   }
 
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+
   while (item == 0) {
     size_t offset;
     size_t distance;
diff --git a/c/enc/hash_forgetful_chain_inc.h b/c/enc/hash_forgetful_chain_inc.h
index 9a8efeb6c..c44276fa4 100644
--- a/c/enc/hash_forgetful_chain_inc.h
+++ b/c/enc/hash_forgetful_chain_inc.h
@@ -212,6 +212,9 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   const uint8_t tiny_hash = (uint8_t)(key);
   out->len = 0;
   out->len_code_delta = 0;
+
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+
   /* Try last distance first. */
   for (i = 0; i < NUM_LAST_DISTANCES_TO_CHECK; ++i) {
     const size_t backward = (size_t)distance_cache[i];
diff --git a/c/enc/hash_longest_match64_inc.h b/c/enc/hash_longest_match64_inc.h
index 8f825de6f..441ab86b4 100644
--- a/c/enc/hash_longest_match64_inc.h
+++ b/c/enc/hash_longest_match64_inc.h
@@ -172,6 +172,9 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   size_t i;
   out->len = 0;
   out->len_code_delta = 0;
+
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+
   /* Try last distance first. */
   for (i = 0; i < (size_t)self->num_last_distances_to_check_; ++i) {
     const size_t backward = (size_t)distance_cache[i];
diff --git a/c/enc/hash_longest_match_inc.h b/c/enc/hash_longest_match_inc.h
index c25cdb0b9..4679dac39 100644
--- a/c/enc/hash_longest_match_inc.h
+++ b/c/enc/hash_longest_match_inc.h
@@ -169,6 +169,9 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   score_t best_score = out->score;
   size_t best_len = out->len;
   size_t i;
+
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+
   out->len = 0;
   out->len_code_delta = 0;
   /* Try last distance first. */
diff --git a/c/enc/hash_longest_match_quickly_inc.h b/c/enc/hash_longest_match_quickly_inc.h
index 1f3602284..57ed586fe 100644
--- a/c/enc/hash_longest_match_quickly_inc.h
+++ b/c/enc/hash_longest_match_quickly_inc.h
@@ -164,6 +164,9 @@ static BROTLI_INLINE void FN(FindLongestMatch)(
   size_t best_len = best_len_in;
   size_t cached_backward = (size_t)distance_cache[0];
   size_t prev_ix = cur_ix - cached_backward;
+
+  BROTLI_DCHECK(cur_ix_masked + max_length <= ring_buffer_mask);
+
   out->len_code_delta = 0;
   if (prev_ix < cur_ix) {
     prev_ix &= (uint32_t)ring_buffer_mask;