diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index 4802543..bfe0ab7 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -2285,7 +2285,7 @@ QPDFWriter::write()
 QPDFObjGen
 QPDFWriter::getRenumberedObjGen(QPDFObjGen og)
 {
-    return QPDFObjGen(m->obj[og].renumber, 0);
+    return {m->obj[og].renumber, 0};
 }
 
 std::map<QPDFObjGen, QPDFXRefEntry>
diff --git a/libqpdf/QPDF_objects.cc b/libqpdf/QPDF_objects.cc
index 3e1f08c..9d02e67 100644
--- a/libqpdf/QPDF_objects.cc
+++ b/libqpdf/QPDF_objects.cc
@@ -1807,7 +1807,7 @@ QPDF::nextObjGen()
     if (max_objid == std::numeric_limits<int>::max()) {
         throw std::range_error("max object id is too high to create new objects");
     }
-    return QPDFObjGen(max_objid + 1, 0);
+    return {max_objid + 1, 0};
 }
 
 QPDFObjectHandle
diff --git a/libqpdf/qpdf/QPDFCrypto_native.hh b/libqpdf/qpdf/QPDFCrypto_native.hh
index 9ac0d75..0ca4b37 100644
--- a/libqpdf/qpdf/QPDFCrypto_native.hh
+++ b/libqpdf/qpdf/QPDFCrypto_native.hh
@@ -23,7 +23,8 @@ class QPDFCrypto_native final: public QPDFCryptoImpl
     void MD5_digest(MD5_Digest) final;
 
     void RC4_init(unsigned char const* key_data, int key_len = -1) final;
-    void RC4_process(unsigned char const* in_data, size_t len, unsigned char* out_data = 0) final;
+    void
+    RC4_process(unsigned char const* in_data, size_t len, unsigned char* out_data = nullptr) final;
     void RC4_finalize() final;
 
     void SHA2_init(int bits) final;
diff --git a/libqpdf/qpdf/RC4_native.hh b/libqpdf/qpdf/RC4_native.hh
index 7607c0c..67bdd03 100644
--- a/libqpdf/qpdf/RC4_native.hh
+++ b/libqpdf/qpdf/RC4_native.hh
@@ -10,7 +10,7 @@ class RC4_native
     RC4_native(unsigned char const* key_data, int key_len = -1);
 
     // out_data = 0 means to encrypt/decrypt in place
-    void process(unsigned char const* in_data, size_t len, unsigned char* out_data = 0);
+    void process(unsigned char const* in_data, size_t len, unsigned char* out_data = nullptr);
 
   private:
     class RC4Key
diff --git a/libtests/crypto_provider.cc b/libtests/crypto_provider.cc
index f28f163..2cebb15 100644
--- a/libtests/crypto_provider.cc
+++ b/libtests/crypto_provider.cc
@@ -47,7 +47,7 @@ class Potato: public QPDFCryptoImpl
     std::string
     SHA2_digest() override
     {
-        return std::string();
+        return {};
     }
     void
     RC4_init(const unsigned char* key_data, int key_len) override