diff --git a/cov/src/graph.rs b/cov/src/graph.rs
index 62a15c3..d95596f 100644
--- a/cov/src/graph.rs
+++ b/cov/src/graph.rs
@@ -12,7 +12,7 @@ use petgraph::Direction;
 use petgraph::graph::{DiGraph, EdgeIndex, EdgeReference, NodeIndex};
 use petgraph::visit::{Dfs, EdgeFiltered, EdgeRef, IntoNodeReferences};
 
-use std::{io, mem, usize};
+use std::{cmp, io, mem, usize};
 use std::borrow::Cow;
 use std::collections::{BTreeMap, Bound, HashSet};
 use std::collections::hash_map::{Entry, HashMap};
@@ -261,7 +261,7 @@ impl Graph {
         for (filename, line_number) in block.iter_lines() {
             let file = r.files.entry(filename).or_default();
             let line = file.lines.entry(line_number).or_default();
-            line.count += block_count;
+            line.count = cmp::max(line.count, block_count);
             line.attr |= block.attr;
             last_line = Some((filename, line_number));
         }
diff --git a/cov/test-data/branches.rustc/x.json b/cov/test-data/branches.rustc/x.json
index 1bedd3c..6512e33 100644
--- a/cov/test-data/branches.rustc/x.json
+++ b/cov/test-data/branches.rustc/x.json
@@ -78,7 +78,7 @@
                     "branches": []
                 },
                 "8": {
-                    "count": 2,
+                    "count": 1,
                     "attr": 0,
                     "branches": [
                         {
@@ -98,12 +98,12 @@
                     ]
                 },
                 "9": {
-                    "count": 2,
+                    "count": 1,
                     "attr": 0,
                     "branches": []
                 },
                 "10": {
-                    "count": 2,
+                    "count": 1,
                     "attr": 0,
                     "branches": [
                         {
diff --git a/cov/test-data/trivial.clang/x.json b/cov/test-data/trivial.clang/x.json
index 73c0a3f..f3c0119 100644
--- a/cov/test-data/trivial.clang/x.json
+++ b/cov/test-data/trivial.clang/x.json
@@ -3,7 +3,7 @@
         "x.cpp": {
             "lines": {
                 "1": {
-                    "count": 2,
+                    "count": 1,
                     "attr": 0,
                     "branches": []
                 }
diff --git a/cov/test-data/trivial.rustc/x.json b/cov/test-data/trivial.rustc/x.json
index 167211e..df54df1 100644
--- a/cov/test-data/trivial.rustc/x.json
+++ b/cov/test-data/trivial.rustc/x.json
@@ -3,7 +3,7 @@
         "x.rs": {
             "lines": {
                 "1": {
-                    "count": 2,
+                    "count": 1,
                     "attr": 0,
                     "branches": []
                 }