diff --git a/src/db-copy.cpp b/src/db-copy.cpp
index a58a9aea3..96fcf8c18 100644
--- a/src/db-copy.cpp
+++ b/src/db-copy.cpp
@@ -7,13 +7,17 @@
  * For a full list of authors see the git log.
  */
 
-#include <cassert>
-
 #include "db-copy.hpp"
+
 #include "format.hpp"
 #include "logging.hpp"
 #include "pgsql.hpp"
 
+#include <cassert>
+#include <cstdlib>
+#include <iterator>
+#include <stdexcept>
+
 void db_deleter_by_id_t::delete_rows(std::string const &table,
                                      std::string const &column,
                                      pg_conn_t const &db_connection)
diff --git a/src/db-copy.hpp b/src/db-copy.hpp
index bd5946a0d..beebc8155 100644
--- a/src/db-copy.hpp
+++ b/src/db-copy.hpp
@@ -10,6 +10,10 @@
  * For a full list of authors see the git log.
  */
 
+#include "osmtypes.hpp"
+#include "pgsql.hpp"
+#include "pgsql-params.hpp"
+
 #include <cassert>
 #include <condition_variable>
 #include <deque>
@@ -22,9 +26,6 @@
 #include <variant>
 #include <vector>
 
-#include "osmtypes.hpp"
-#include "pgsql.hpp"
-
 /**
  * Table information necessary for building SQL queries.
  */
diff --git a/src/debug-output.cpp b/src/debug-output.cpp
index 3ee119d2c..c8a94d19b 100644
--- a/src/debug-output.cpp
+++ b/src/debug-output.cpp
@@ -9,6 +9,8 @@
 
 #include "debug-output.hpp"
 
+#include "expire-output.hpp"
+#include "flex-table.hpp"
 #include "logging.hpp"
 
 void write_expire_output_list_to_debug_log(
diff --git a/src/debug-output.hpp b/src/debug-output.hpp
index e4777221e..96256a5d7 100644
--- a/src/debug-output.hpp
+++ b/src/debug-output.hpp
@@ -10,8 +10,10 @@
  * For a full list of authors see the git log.
  */
 
-#include "expire-output.hpp"
-#include "flex-table.hpp"
+#include <vector>
+
+class expire_output_t;
+class flex_table_t;
 
 void write_expire_output_list_to_debug_log(
     std::vector<expire_output_t> const &expire_outputs);
diff --git a/src/expire-output.cpp b/src/expire-output.cpp
index 68d2ac372..5ec48d9f2 100644
--- a/src/expire-output.cpp
+++ b/src/expire-output.cpp
@@ -14,6 +14,7 @@
 #include "pgsql.hpp"
 #include "tile.hpp"
 
+#include <cerrno>
 #include <system_error>
 
 std::size_t
diff --git a/src/expire-output.hpp b/src/expire-output.hpp
index 1c9821617..cbfa92869 100644
--- a/src/expire-output.hpp
+++ b/src/expire-output.hpp
@@ -13,6 +13,7 @@
 #include "tile.hpp"
 
 #include <cassert>
+#include <cstddef>
 #include <cstdint>
 #include <string>
 #include <utility>
diff --git a/src/flex-lua-index.cpp b/src/flex-lua-index.cpp
index 085b360f5..5db9db648 100644
--- a/src/flex-lua-index.cpp
+++ b/src/flex-lua-index.cpp
@@ -8,11 +8,15 @@
  */
 
 #include "flex-lua-index.hpp"
+
+#include "flex-index.hpp"
+#include "flex-table.hpp"
+#include "format.hpp"
 #include "lua-utils.hpp"
-#include "output-flex.hpp"
 #include "pgsql-capabilities.hpp"
 #include "util.hpp"
 
+#include <stdexcept>
 #include <string>
 #include <vector>
 
diff --git a/src/flex-table-column.cpp b/src/flex-table-column.cpp
index 489cd722e..7cf561dbc 100644
--- a/src/flex-table-column.cpp
+++ b/src/flex-table-column.cpp
@@ -13,7 +13,6 @@
 #include "pgsql-capabilities.hpp"
 #include "util.hpp"
 
-#include <algorithm>
 #include <cassert>
 #include <cctype>
 #include <cstdlib>
diff --git a/src/flex-table.hpp b/src/flex-table.hpp
index 4973fe20a..f45b0057c 100644
--- a/src/flex-table.hpp
+++ b/src/flex-table.hpp
@@ -20,7 +20,10 @@
 
 #include <osmium/osm/item_type.hpp>
 
+#include <cassert>
+#include <chrono>
 #include <cstddef>
+#include <future>
 #include <limits>
 #include <memory>
 #include <string>
diff --git a/src/flex-write.hpp b/src/flex-write.hpp
index 999923530..a8536d4fa 100644
--- a/src/flex-write.hpp
+++ b/src/flex-write.hpp
@@ -10,12 +10,15 @@
  * For a full list of authors see the git log.
  */
 
-#include "expire-tiles.hpp"
 #include "flex-table.hpp"
 
 #include <lua.hpp>
 
 #include <stdexcept>
+#include <string>
+#include <vector>
+
+class expire_tiles;
 
 class not_null_exception : public std::runtime_error
 {
diff --git a/src/gen/canvas.cpp b/src/gen/canvas.cpp
index 8978c4ffc..e88095563 100644
--- a/src/gen/canvas.cpp
+++ b/src/gen/canvas.cpp
@@ -10,10 +10,13 @@
 #include "canvas.hpp"
 
 #include "raster.hpp"
+#include "tile.hpp"
 
 #include <opencv2/imgcodecs.hpp>
 #include <opencv2/imgproc.hpp>
 
+#include <cassert>
+
 void canvas_t::open_close(unsigned int buffer_size)
 {
     auto const kernel1 = cv::getStructuringElement(
diff --git a/src/gen/canvas.hpp b/src/gen/canvas.hpp
index c184af827..5ccaa906d 100644
--- a/src/gen/canvas.hpp
+++ b/src/gen/canvas.hpp
@@ -11,11 +11,14 @@
  */
 
 #include "geom.hpp"
-#include "tile.hpp"
 
 #include <opencv2/core.hpp>
 
 #include <cstddef>
+#include <string>
+#include <vector>
+
+class tile_t;
 
 /**
  * This class wraps the image class from the OpenCV library.
diff --git a/src/gen/gen-base.cpp b/src/gen/gen-base.cpp
index d883eb1e2..f71c13f9b 100644
--- a/src/gen/gen-base.cpp
+++ b/src/gen/gen-base.cpp
@@ -14,6 +14,8 @@
 
 #include <fmt/args.h>
 
+#include <cassert>
+
 gen_base_t::gen_base_t(pg_conn_t *connection, bool append, params_t *params)
 : m_connection(connection), m_params(params), m_append(append)
 {
diff --git a/src/gen/gen-base.hpp b/src/gen/gen-base.hpp
index 3117b968c..90e8ae37f 100644
--- a/src/gen/gen-base.hpp
+++ b/src/gen/gen-base.hpp
@@ -17,6 +17,7 @@
 #include <cstdint>
 #include <cstdlib>
 #include <string>
+#include <string_view>
 #include <vector>
 
 class params_t;
diff --git a/src/gen/gen-create.cpp b/src/gen/gen-create.cpp
index 195f59c16..32d6487ad 100644
--- a/src/gen/gen-create.cpp
+++ b/src/gen/gen-create.cpp
@@ -9,6 +9,8 @@
 
 #include "gen-create.hpp"
 
+#include "format.hpp"
+#include "gen-base.hpp"
 #include "gen-discrete-isolation.hpp"
 #include "gen-rivers.hpp"
 #include "gen-tile-builtup.hpp"
diff --git a/src/gen/gen-create.hpp b/src/gen/gen-create.hpp
index b7997bb3c..a445a9455 100644
--- a/src/gen/gen-create.hpp
+++ b/src/gen/gen-create.hpp
@@ -10,11 +10,10 @@
  * For a full list of authors see the git log.
  */
 
-#include "gen-base.hpp"
-
 #include <memory>
 #include <string>
 
+class gen_base_t;
 class params_t;
 class pg_conn_t;
 
diff --git a/src/gen/gen-discrete-isolation.cpp b/src/gen/gen-discrete-isolation.cpp
index a713091c9..6c8ca8a55 100644
--- a/src/gen/gen-discrete-isolation.cpp
+++ b/src/gen/gen-discrete-isolation.cpp
@@ -9,12 +9,14 @@
 
 #include "gen-discrete-isolation.hpp"
 
-#include "logging.hpp"
 #include "params.hpp"
 #include "pgsql.hpp"
 #include "util.hpp"
 
 #include <algorithm>
+#include <cmath>
+#include <cstdint>
+#include <cstdlib>
 #include <vector>
 
 gen_di_t::gen_di_t(pg_conn_t *connection, bool append, params_t *params)
@@ -115,7 +117,7 @@ FROM {src} WHERE {importance_column} > 0
                     min = dist;
                 }
             }
-            data[n].di = sqrt(min);
+            data[n].di = std::sqrt(min);
         }
         data[0].di = data[1].di + 1;
     }
diff --git a/src/gen/gen-discrete-isolation.hpp b/src/gen/gen-discrete-isolation.hpp
index 29d680b9a..d6d5c2725 100644
--- a/src/gen/gen-discrete-isolation.hpp
+++ b/src/gen/gen-discrete-isolation.hpp
@@ -12,8 +12,12 @@
 
 #include "gen-base.hpp"
 
+#include <cstddef>
 #include <string_view>
 
+class params_t;
+class pg_conn_t;
+
 class gen_di_t : public gen_base_t
 {
 public:
diff --git a/src/gen/gen-rivers.hpp b/src/gen/gen-rivers.hpp
index 3cd351ce5..513da5786 100644
--- a/src/gen/gen-rivers.hpp
+++ b/src/gen/gen-rivers.hpp
@@ -12,8 +12,12 @@
 
 #include "gen-base.hpp"
 
+#include <cstddef>
 #include <string_view>
 
+class params_t;
+class pg_conn_t;
+
 class gen_rivers_t : public gen_base_t
 {
 public:
diff --git a/src/gen/osm2pgsql-gen.cpp b/src/gen/osm2pgsql-gen.cpp
index c3292da22..5ba2b245a 100644
--- a/src/gen/osm2pgsql-gen.cpp
+++ b/src/gen/osm2pgsql-gen.cpp
@@ -15,7 +15,6 @@
  * in the future.
  */
 
-#include "canvas.hpp"
 #include "command-line-app.hpp"
 #include "debug-output.hpp"
 #include "expire-output.hpp"
@@ -30,7 +29,6 @@
 #include "lua-init.hpp"
 #include "lua-setup.hpp"
 #include "lua-utils.hpp"
-#include "options.hpp"
 #include "params.hpp"
 #include "pgsql-capabilities.hpp"
 #include "pgsql.hpp"
@@ -45,18 +43,16 @@
 #include <lua.hpp>
 
 #include <algorithm>
-#include <array>
 #include <atomic>
-#include <cassert>
 #include <chrono>
 #include <cstdint>
 #include <cstdlib>
-#include <cstring>
-#include <getopt.h>
-#include <limits>
+#include <memory>
+#include <mutex>
 #include <stdexcept>
 #include <string>
 #include <thread>
+#include <vector>
 
 // Lua can't call functions on C++ objects directly. This macro defines simple
 // C "trampoline" functions which are called from Lua which get the current
diff --git a/src/gen/tracer.cpp b/src/gen/tracer.cpp
index 027fb3415..7673bf024 100644
--- a/src/gen/tracer.cpp
+++ b/src/gen/tracer.cpp
@@ -9,7 +9,9 @@
 
 #include "tracer.hpp"
 
+#include "canvas.hpp"
 #include "geom-boost-adaptor.hpp"
+#include "tile.hpp"
 
 #include <cassert>
 #include <cmath>
diff --git a/src/gen/tracer.hpp b/src/gen/tracer.hpp
index 141cdea93..d07910883 100644
--- a/src/gen/tracer.hpp
+++ b/src/gen/tracer.hpp
@@ -10,15 +10,17 @@
  * For a full list of authors see the git log.
  */
 
-#include "canvas.hpp"
 #include "geom.hpp"
-#include "tile.hpp"
 
 #include <potracelib.h>
 
+#include <cstddef>
 #include <memory>
 #include <vector>
 
+class canvas_t;
+class tile_t;
+
 class tracer_t
 {
 public:
diff --git a/src/geom-box.cpp b/src/geom-box.cpp
index a5f8217fd..9393e8ce8 100644
--- a/src/geom-box.cpp
+++ b/src/geom-box.cpp
@@ -9,6 +9,8 @@
 
 #include "geom-box.hpp"
 
+#include <variant>
+
 namespace geom {
 
 box_t &box_t::extend(point_t const &point) noexcept
diff --git a/src/geom-from-osm.cpp b/src/geom-from-osm.cpp
index 71f858f12..3cfd98441 100644
--- a/src/geom-from-osm.cpp
+++ b/src/geom-from-osm.cpp
@@ -13,6 +13,7 @@
 #include <osmium/area/geom_assembler.hpp>
 #include <osmium/osm/way.hpp>
 
+#include <cassert>
 #include <utility>
 
 namespace geom {
diff --git a/src/geom-functions.hpp b/src/geom-functions.hpp
index 51e122ed4..1048a6b8e 100644
--- a/src/geom-functions.hpp
+++ b/src/geom-functions.hpp
@@ -13,6 +13,8 @@
 #include "geom.hpp"
 #include "reprojection.hpp"
 
+#include <cassert>
+#include <cstddef>
 #include <string_view>
 #include <utility>
 #include <vector>
diff --git a/src/lua-utils.cpp b/src/lua-utils.cpp
index 1a28f346b..ee047f9b5 100644
--- a/src/lua-utils.cpp
+++ b/src/lua-utils.cpp
@@ -12,7 +12,6 @@
 #include "format.hpp"
 
 #include <cassert>
-#include <stdexcept>
 
 // The lua_getextraspace() function is only available from Lua 5.3. For
 // earlier versions we fall back to storing the context pointer in the
diff --git a/src/middle-ram.hpp b/src/middle-ram.hpp
index a595104bc..935491012 100644
--- a/src/middle-ram.hpp
+++ b/src/middle-ram.hpp
@@ -19,6 +19,7 @@
 #include <osmium/memory/buffer.hpp>
 #include <osmium/osm.hpp>
 
+#include <cassert>
 #include <cstddef>
 #include <memory>
 #include <string>
diff --git a/src/node-persistent-cache.cpp b/src/node-persistent-cache.cpp
index 6b06b1ceb..7cd97b8c3 100644
--- a/src/node-persistent-cache.cpp
+++ b/src/node-persistent-cache.cpp
@@ -11,8 +11,9 @@
 #include "node-persistent-cache.hpp"
 
 #include <cassert>
-#include <stdexcept>
+#include <cerrno>
 #include <system_error>
+#include <utility>
 
 void node_persistent_cache::set(osmid_t id, osmium::Location location)
 {
diff --git a/src/osm2pgsql.cpp b/src/osm2pgsql.cpp
index 26bdc47f7..b3178e1e6 100644
--- a/src/osm2pgsql.cpp
+++ b/src/osm2pgsql.cpp
@@ -16,7 +16,6 @@
 #include "output.hpp"
 #include "pgsql.hpp"
 #include "pgsql-capabilities.hpp"
-#include "pgsql-helper.hpp"
 #include "properties.hpp"
 #include "util.hpp"
 #include "version.hpp"
@@ -26,6 +25,7 @@
 #include <exception>
 #include <filesystem>
 #include <memory>
+#include <string>
 #include <utility>
 
 namespace {
diff --git a/src/table.cpp b/src/table.cpp
index 229e7b160..9d707497f 100644
--- a/src/table.cpp
+++ b/src/table.cpp
@@ -8,11 +8,9 @@
  */
 
 #include <algorithm>
-#include <cassert>
 #include <cstdint>
 #include <cstdio>
 #include <limits>
-#include <stdexcept>
 #include <string>
 #include <vector>