diff --git a/src/Formats/MarkInCompressedFile.cpp b/src/Formats/MarkInCompressedFile.cpp
index fd17525d793..f305fbfa0ac 100644
--- a/src/Formats/MarkInCompressedFile.cpp
+++ b/src/Formats/MarkInCompressedFile.cpp
@@ -63,7 +63,7 @@ MarksInCompressedFile::MarksInCompressedFile(const PlainArray & marks)
 
     // Overallocate by +1 element to let the bit packing/unpacking do less bounds checking.
     size_t packed_length = (packed_bits + 63) / 64 + 1;
-    packed.reserve(packed_length);
+    packed.reserve_exact(packed_length);
     packed.resize_fill(packed_length);
 
     // Second pass: write out the packed marks.
diff --git a/src/Formats/tests/gtest_marks.cpp b/src/Formats/tests/gtest_marks.cpp
index 334e99d2ec6..47ec0eea46c 100644
--- a/src/Formats/tests/gtest_marks.cpp
+++ b/src/Formats/tests/gtest_marks.cpp
@@ -35,18 +35,29 @@ TEST(Marks, Compression)
         EXPECT_LE((marks.approximateMemoryUsage() - sizeof(MarksInCompressedFile)) * 8, plain.size() * max_bits_per_mark);
     };
 
-    // Typical.
-    test(gen(10000, 1'000'000, 0), 30);
+    {
+        SCOPED_TRACE("Typical");
+        test(gen(10000, 1'000'000, 0), 30);
+    }
 
-    // Completely random 64-bit values.
-    test(gen(10000, UINT64_MAX - 1, UINT64_MAX - 1), 130);
 
-    // All zeros.
-    test(gen(10000, 0, 0), 2);
+    {
+        SCOPED_TRACE("Completely random 64-bit values");
+        test(gen(10000, UINT64_MAX - 1, UINT64_MAX - 1), 130);
+    }
 
-    // Short.
-    test(gen(10, 1000, 1000), 65);
+    {
+        SCOPED_TRACE("All zeros");
+        test(gen(10000, 0, 0), 2);
+    }
 
-    // Empty.
-    test(gen(0, 0, 0), 0);
+    {
+        SCOPED_TRACE("Short");
+        test(gen(10, 1000, 1000), 65);
+    }
+
+    {
+        SCOPED_TRACE("Empty");
+        test(gen(0, 0, 0), 0);
+    }
 }