diff --git a/src/collocatordb.cc b/src/collocatordb.cc
index 4da2e06..6eda410 100644
--- a/src/collocatordb.cc
+++ b/src/collocatordb.cc
@@ -859,7 +859,12 @@
   /* fixed size, so it lives on the stack and cannot be leaked */
   uint64_t sumWindow[2 * WINDOW_SIZE];
   memset(sumWindow, 0, sizeof(sumWindow));
-  int true_window_size = 1;
+  /* Counted up from zero, since the first key of the iteration takes the same
+     branch as any further key of the same collocate, which increments it. It
+     used to start at one, so that the first collocate of every query was scored
+     with a window one position too wide, which inflated its expected frequency
+     and thus lowered its pmi, npmi, md, lfmd and llr. */
+  int true_window_size = 0;
   int usedPositions = 0;
 
   if (w1 > _vocab.size()) {
diff --git a/tests/basic_test.c b/tests/basic_test.c
index 53e2736..d98aac4 100644
--- a/tests/basic_test.c
+++ b/tests/basic_test.c
@@ -28,7 +28,7 @@
 void test_collocation_scores() {
   COLLOCATORDB* cdb = open_collocatordb(dbpath);
   TEST_ASSERT(cdb != NULL);
-  char *expected = " { \"f1\": 217,\"w1\":\"Aluminium\", \"N\": 152743, \"collocates\": [{\"word\":\"Anwendungstechnologie\",\"f2\":16,\"f\":16,\"npmi\":0.594849,\"pmi\":8.4592,\"llr\":188.227,\"lfmd\":16.4592,\"md\":12.4592,\"md_nws\":10.1373,\"dice\":0.137339,\"ld\":11.1358,\"ln_count\":16,\"rn_count\":0,\"ln_pmi\":9.4592,\"rn_pmi\":-1,\"ldaf\":11.1358,\"win\":32,\"afwin\":32}]}\n";
+  char *expected = " { \"f1\": 217,\"w1\":\"Aluminium\", \"N\": 152743, \"collocates\": [{\"word\":\"Anwendungstechnologie\",\"f2\":16,\"f\":16,\"npmi\":0.715481,\"pmi\":9.4592,\"llr\":211.02,\"lfmd\":17.4592,\"md\":13.4592,\"md_nws\":10.1373,\"dice\":0.137339,\"ld\":11.1358,\"ln_count\":16,\"rn_count\":0,\"ln_pmi\":9.4592,\"rn_pmi\":-1,\"ldaf\":11.1358,\"win\":32,\"afwin\":32}]}\n";
   char *produced = get_collocation_scores_as_json(cdb, 62, 966);
   TEST_CHECK(strcmp(produced, expected) == 0);
   TEST_MSG("Expected: %s", expected);