diff --git a/.clang-tidy b/.clang-tidy
index 897b30f2ab..4d9daefbad 100644
--- a/.clang-tidy
+++ b/.clang-tidy
@@ -9,6 +9,7 @@ Checks: [-*,
          modernize-redundant-void-arg,
          modernize-return-braced-init-list,
          modernize-use-bool-literals,
+         modernize-use-default-member-init,
 
          # Enable a very limited number of the cppcoreguidelines checkers.
          # See the notes for some of the rest of them below.
diff --git a/src/Reassem.cc b/src/Reassem.cc
index e4fdf7fd8c..7efa34b42d 100644
--- a/src/Reassem.cc
+++ b/src/Reassem.cc
@@ -243,12 +243,7 @@ uint64_t DataBlockList::Trim(uint64_t seq, uint64_t max_old, DataBlockList* old_
 }
 
 Reassembler::Reassembler(uint64_t init_seq, ReassemblerType reassem_type)
-    : block_list(this),
-      old_block_list(this),
-      last_reassem_seq(init_seq),
-      trim_seq(init_seq),
-      max_old_blocks(0),
-      rtype(reassem_type) {}
+    : block_list(this), old_block_list(this), last_reassem_seq(init_seq), trim_seq(init_seq), rtype(reassem_type) {}
 
 void Reassembler::CheckOverlap(const DataBlockList& list, uint64_t seq, uint64_t len, const u_char* data) {
     if ( list.Empty() )
diff --git a/src/file_analysis/FileReassembler.cc b/src/file_analysis/FileReassembler.cc
index 7745bcdc75..fae2626451 100644
--- a/src/file_analysis/FileReassembler.cc
+++ b/src/file_analysis/FileReassembler.cc
@@ -11,7 +11,7 @@ namespace zeek::file_analysis {
 class File;
 
 FileReassembler::FileReassembler(File* f, uint64_t starting_offset)
-    : Reassembler(starting_offset, REASSEM_FILE), the_file(f), flushing(false) {}
+    : Reassembler(starting_offset, REASSEM_FILE), the_file(f) {}
 
 uint64_t FileReassembler::Flush() {
     if ( flushing )
diff --git a/src/input/Manager.cc b/src/input/Manager.cc
index 03e4b6bde0..94eae7490c 100644
--- a/src/input/Manager.cc
+++ b/src/input/Manager.cc
@@ -51,16 +51,16 @@ static void input_hash_delete_func(void* val) {
 class Manager::Stream {
 public:
     string name;
-    bool removed;
+    bool removed = false;
 
     StreamType stream_type; // to distinguish between event and table streams
 
-    EnumVal* type;
-    ReaderFrontend* reader;
-    TableVal* config;
+    EnumVal* type = nullptr;
+    ReaderFrontend* reader = nullptr;
+    TableVal* config = nullptr;
     EventHandlerPtr error_event;
 
-    RecordVal* description;
+    RecordVal* description = nullptr;
 
     virtual ~Stream();
 
@@ -68,8 +68,7 @@ protected:
     Stream(StreamType t);
 };
 
-Manager::Stream::Stream(StreamType t)
-    : name(), removed(), stream_type(t), type(), reader(), config(), error_event(), description() {}
+Manager::Stream::Stream(StreamType t) : stream_type(t) {}
 
 Manager::Stream::~Stream() {
     Unref(type);
@@ -80,18 +79,18 @@ Manager::Stream::~Stream() {
 
 class Manager::TableStream final : public Manager::Stream {
 public:
-    unsigned int num_idx_fields;
-    unsigned int num_val_fields;
-    bool want_record;
+    unsigned int num_idx_fields = 0;
+    unsigned int num_val_fields = 0;
+    bool want_record = false;
 
-    TableVal* tab;
-    RecordType* rtype;
-    RecordType* itype;
+    TableVal* tab = nullptr;
+    RecordType* rtype = nullptr;
+    RecordType* itype = nullptr;
 
-    PDict<InputHash>* currDict;
-    PDict<InputHash>* lastDict;
+    PDict<InputHash>* currDict = nullptr;
+    PDict<InputHash>* lastDict = nullptr;
 
-    Func* pred;
+    Func* pred = nullptr;
 
     EventHandlerPtr event;
 
@@ -103,7 +102,7 @@ class Manager::EventStream final : public Manager::Stream {
 public:
     EventHandlerPtr event;
 
-    RecordType* fields;
+    RecordType* fields = nullptr;
     unsigned int num_fields;
 
     bool want_record;
@@ -119,21 +118,9 @@ public:
     ~AnalysisStream() override = default;
 };
 
-Manager::TableStream::TableStream()
-    : Manager::Stream::Stream(TABLE_STREAM),
-      num_idx_fields(),
-      num_val_fields(),
-      want_record(),
-      tab(),
-      rtype(),
-      itype(),
-      currDict(),
-      lastDict(),
-      pred(),
-      event() {}
+Manager::TableStream::TableStream() : Manager::Stream::Stream(TABLE_STREAM) {}
 
-Manager::EventStream::EventStream()
-    : Manager::Stream::Stream(EVENT_STREAM), event(), fields(), num_fields(), want_record() {}
+Manager::EventStream::EventStream() : Manager::Stream::Stream(EVENT_STREAM) {}
 
 Manager::EventStream::~EventStream() {
     if ( fields )