diff --git a/Changelog.md b/Changelog.md
index 33d14e0..9602eaf 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,5 +1,14 @@
 # Changelog
 
+- fixed a crash on out of range word ranks: a single request with a `w`
+  parameter beyond the vocabulary size, or a `getVecsByRanks` request with such
+  a rank, killed the worker process
+- fixed `w2v.merge`, which died at startup with "Undefined subroutine
+  &main::mergeVectors", and the lookup of count based collocators and
+  precomputed profiles for merged models, which used unshifted ranks
+- fixed `getVecsByRanks`, which answered every request with "Undefined
+  subroutine &main::getVecs", so the collocator SOM never got its vectors, and
+  which was only reachable below the `/derekovecs` prefix
 - fixed memory leaks in the request path: per request the server leaked the
   target sum array, the thread handles, the target word list and the
   collocator results of all window threads, plus every string and array
diff --git a/lib/IDS/DeReKoVecs/Read.pm b/lib/IDS/DeReKoVecs/Read.pm
index 0da0cf4..f75ca90 100644
--- a/lib/IDS/DeReKoVecs/Read.pm
+++ b/lib/IDS/DeReKoVecs/Read.pm
@@ -7,7 +7,6 @@
 
 my $src_file      = undef;
 
-our $mergedEnd=0;
 our $opt_p = 5676;
 our $opt_C;
 
@@ -31,7 +30,7 @@
 use Mojo::Cache;
 use Exporter qw(import);
 
-our @EXPORT = qw(init_net load_sprofiles getVocabSize getDowntimeCalendar getCollocationAssociation getClassicCollocatorsCached getSimilarProfiles getSimilarProfilesCached getBiggestMergedDifferences filter_garbage get_neighbours getVecs getWordNumber dump_vecs dump_for_numpy cos_similarity_as_json get_version getPosWiseW2VCollocators configure_cache cache_stats);
+our @EXPORT = qw(init_net load_sprofiles mergeVectors getVocabSize getDowntimeCalendar getCollocationAssociation getClassicCollocatorsCached getSimilarProfiles getSimilarProfilesCached getBiggestMergedDifferences getMergedEnd filter_garbage get_neighbours getVecs getWordNumber dump_vecs dump_for_numpy cos_similarity_as_json get_version getPosWiseW2VCollocators configure_cache cache_stats);
 
 my $cccache = Mojo::Cache->new(max_keys => $CC_CACHE_MAX_KEYS); # classic collocator cache
 my $spcache = Mojo::Cache->new(max_keys => $SP_CACHE_MAX_KEYS); # similar profile cache
@@ -80,8 +79,12 @@
 sub getClassicCollocatorsCached {
   my ($c, $word, $compare_to) = @_;
   my $s2 = "";
-  if($word > $mergedEnd) {
-    $word-=$mergedEnd;
+  # The collocator db is the one of the primary model, which sits at
+  # [merged_end, words) in the merged vocabulary, so its ranks have to be
+  # shifted back before they can be looked up.
+  my $merged_end = getMergedEnd();
+  if($word >= $merged_end) {
+    $word -= $merged_end;
   }
 
   my $pipe;
@@ -133,6 +136,10 @@
 
 sub getSimilarProfilesCached {
   my ($c, $word) = @_;
+  # like the collocator db, the precomputed profiles belong to the primary
+  # model, see getClassicCollocatorsCached()
+  my $merged_end = getMergedEnd();
+  $word -= $merged_end if $word >= $merged_end;
   my $profiles = $opt_C ? undef : $spcache->get($word);
   if(!defined $profiles) {
     $profiles = getSimilarProfiles($word);
diff --git a/lib/IDS/DeReKoVecs/derekovecs-server.c b/lib/IDS/DeReKoVecs/derekovecs-server.c
index 9d073a4..56e037c 100644
--- a/lib/IDS/DeReKoVecs/derekovecs-server.c
+++ b/lib/IDS/DeReKoVecs/derekovecs-server.c
@@ -526,8 +526,11 @@
     if (elem != NULL) {
       long j = (long)SvNV(*elem);
       AV *vector = newAV();
-      for (b = 0; b < size; b++) {
-        av_push(vector, newSVnv(M[b + j * size]));
+      /* ranks come from the request, reading outside the model would crash */
+      if (j >= 0 && j < words) {
+        for (b = 0; b < size; b++) {
+          av_push(vector, newSVnv(M[b + j * size]));
+        }
       }
       av_push(result, newRV_noinc((SV *)vector));
     }
@@ -535,6 +538,13 @@
   return newRV_noinc((SV *)result);
 }
 
+/* Word ids of the collocator db refer to the primary model, which occupies
+   [0, words - merged_end) of its own vocabulary. libcollocatordb crashes on
+   ids outside that range, and the ids come straight from the request. */
+int valid_cdb_node(long node) {
+  return cdb != NULL && node >= 0 && node < words - merged_end;
+}
+
 /* All functions handing a string back to perl return an SV*, because for a
    char* return value Inline::C only copies the string into the return SV and
    never frees the buffer we allocated here. */
@@ -544,7 +554,7 @@
   char pair_buffer[2048];
   buffer[0] = '[';
   buffer[1] = 0;
-  if (node >= sprofiles_qty) {
+  if (node < 0 || node >= sprofiles_qty) {
     printf("Not available in precomputed profile\n");
     return newSVpv("[{\"w\":\"not available\", \"v\":0}]\n", 0);
   }
@@ -566,15 +576,21 @@
 
 /* get_collocat*_as_json() hand out strdup()ed buffers that we own. */
 SV *getCollocationScores(long node, long collocate) {
-  char *json = (cdb ? (char *)get_collocation_scores_as_json(cdb, node, collocate) : NULL);
-  SV *res = newSVpv(json ? json : "[]", 0);
+  char *json = NULL;
+  SV *res;
+  if (valid_cdb_node(node) && valid_cdb_node(collocate))
+    json = (char *)get_collocation_scores_as_json(cdb, node, collocate);
+  res = newSVpv(json ? json : "{\"collocates\":[]}", 0);
   free(json);
   return res;
 }
 
 SV *getClassicCollocators(long node) {
-  char *json = (cdb ? (char *)get_collocators_as_json(cdb, node) : NULL);
-  SV *res = newSVpv(json ? json : "[]", 0);
+  char *json = NULL;
+  SV *res;
+  if (valid_cdb_node(node))
+    json = (char *)get_collocators_as_json(cdb, node);
+  res = newSVpv(json ? json : "{\"collocates\":[]}", 0);
   free(json);
   return res;
 }
@@ -1279,3 +1295,11 @@
 unsigned long getVocabSize() {
   return (unsigned long) words;
 }
+
+/* First rank of the primary model in the merged vocabulary, 0 if no second
+   model was merged in. mergeVectors() puts the merged in model at ranks
+   [0, merged_end) and the primary model - the one the collocator db belongs
+   to - at [merged_end, words). */
+long getMergedEnd() {
+  return (long) merged_end;
+}