diff --git a/src/db-copy.hpp b/src/db-copy.hpp
index 6a6e46bd1..f843aad8a 100644
--- a/src/db-copy.hpp
+++ b/src/db-copy.hpp
@@ -15,6 +15,7 @@
 #include "pgsql-params.hpp"
 
 #include <cassert>
+#include <cstddef>
 #include <condition_variable>
 #include <deque>
 #include <future>
@@ -74,12 +75,11 @@ class db_target_descr_t
  */
 class db_deleter_by_id_t
 {
-    enum
-    {
-        // There is a trade-off here between sending as few DELETE SQL as
-        // possible and keeping the size of the deletable vector managable.
-        Max_entries = 1000000
-    };
+    /**
+     * There is a trade-off here between sending as few DELETE SQL as
+     * possible and keeping the size of the deletable vector managable.
+     */
+    static constexpr std::size_t Max_entries = 1000000;
 
 public:
     bool has_data() const noexcept { return !m_deletables.empty(); }
@@ -101,12 +101,11 @@ class db_deleter_by_id_t
  */
 class db_deleter_by_type_and_id_t
 {
-    enum
-    {
-        // There is a trade-off here between sending as few DELETE SQL as
-        // possible and keeping the size of the deletable vector managable.
-        Max_entries = 1000000
-    };
+    /**
+     * There is a trade-off here between sending as few DELETE SQL as
+     * possible and keeping the size of the deletable vector managable.
+     */
+    static constexpr std::size_t Max_entries = 1000000;
 
     struct item_t
     {
@@ -140,23 +139,23 @@ class db_deleter_by_type_and_id_t
 
 struct db_cmd_copy_t
 {
-    enum
-    {
-        /** Size of a single buffer with COPY data for Postgresql.
-         *  This is a trade-off between memory usage and sending large chunks
-         *  to speed up processing. Currently a one-size fits all value.
-         *  Needs more testing and individual values per queue.
-         */
-        Max_buf_size = 10 * 1024 * 1024,
-        /** Maximum length of the queue with COPY data.
-         *  In the usual case, PostgreSQL should be faster processing the
-         *  data than it can be produced and there should only be one element
-         *  in the queue. If PostgreSQL is slower, then the queue will always
-         *  be full and it is better to keep the queue smaller to reduce memory
-         *  usage. Current value is just assumed to be a reasonable trade off.
-         */
-        Max_buffers = 10
-    };
+    /**
+     * Size of a single buffer with COPY data for Postgresql.
+     * This is a trade-off between memory usage and sending large chunks
+     * to speed up processing. Currently a one-size fits all value.
+     * Needs more testing and individual values per queue.
+     */
+    static constexpr std::size_t Max_buf_size = 10 * 1024 * 1024;
+
+    /**
+     * Maximum length of the queue with COPY data.
+     * In the usual case, PostgreSQL should be faster processing the
+     * data than it can be produced and there should only be one element
+     * in the queue. If PostgreSQL is slower, then the queue will always
+     * be full and it is better to keep the queue smaller to reduce memory
+     * usage. Current value is just assumed to be a reasonable trade off.
+     */
+    static constexpr std::size_t Max_buffers = 10;
 
     /// Name of the target table for the copy operation
     std::shared_ptr<db_target_descr_t> target;
diff --git a/src/middle-pgsql.cpp b/src/middle-pgsql.cpp
index 7bae3ec67..8aa2194ea 100644
--- a/src/middle-pgsql.cpp
+++ b/src/middle-pgsql.cpp
@@ -235,18 +235,18 @@ class member_list_json_builder
     }
 
 private:
-    osmium::builder::RelationMemberListBuilder *m_builder;
     std::string m_role;
+    osmium::builder::RelationMemberListBuilder *m_builder;
     osmium::object_id_type m_ref = 0;
     osmium::item_type m_type = osmium::item_type::undefined;
-    enum class next_val
+    enum class next_val : std::uint8_t
     {
         none,
         type,
         ref,
         role
     } m_next_val = next_val::none;
-};
+}; // class member_list_json_builder
 
 template <typename T>
 void pgsql_parse_json_members(char const *string,
diff --git a/src/output-flex.hpp b/src/output-flex.hpp
index c803d3a30..23dceab08 100644
--- a/src/output-flex.hpp
+++ b/src/output-flex.hpp
@@ -40,7 +40,7 @@ struct options_t;
  * When C++ code is called from the Lua code we sometimes need to know
  * in what context this happens. These are the possible contexts.
  */
-enum class calling_context
+enum class calling_context : std::uint8_t
 {
     main = 0, ///< In main context, i.e. the Lua script outside any callbacks
     process_node = 1, ///< In the process_node() callback
diff --git a/src/taginfo.hpp b/src/taginfo.hpp
index 75fcbefb0..75977541e 100644
--- a/src/taginfo.hpp
+++ b/src/taginfo.hpp
@@ -10,10 +10,11 @@
  * For a full list of authors see the git log.
  */
 
+#include <cstdint>
 #include <string>
 #include <vector>
 
-enum class ColumnType
+enum class ColumnType : std::uint8_t
 {
     INT,
     REAL,
diff --git a/tests/test-output-flex-nodes.cpp b/tests/test-output-flex-nodes.cpp
index 80d9ba732..3dae49be8 100644
--- a/tests/test-output-flex-nodes.cpp
+++ b/tests/test-output-flex-nodes.cpp
@@ -53,7 +53,7 @@ TEST_CASE("add nodes")
     CHECK(1 == conn.get_count("osm2pgsql_test_t1", "node_id = 17"));
 }
 
-enum class node_relationship
+enum class node_relationship : std::uint8_t
 {
     none,
     in_way,