diff --git a/src/bin/initdb/Makefile b/src/bin/initdb/Makefile
index d69bd89572..e80e57e457 100644
--- a/src/bin/initdb/Makefile
+++ b/src/bin/initdb/Makefile
@@ -16,13 +16,12 @@ subdir = src/bin/initdb
 top_builddir = ../../..
 include $(top_builddir)/src/Makefile.global
 
-override CPPFLAGS := -I$(libpq_srcdir) -I$(top_srcdir)/src/timezone $(ICU_CFLAGS) $(CPPFLAGS)
-
 # Note: it's important that we link to encnames.o from libpgcommon, not
 # from libpq, else we have risks of version skew if we run with a libpq
-# shared library from a different PG version.  The libpq_pgport macro
-# should ensure that that happens.
-#
+# shared library from a different PG version.  Define
+# USE_PRIVATE_ENCODING_FUNCS to ensure that that happens.
+override CPPFLAGS := -DUSE_PRIVATE_ENCODING_FUNCS -I$(libpq_srcdir) -I$(top_srcdir)/src/timezone $(ICU_CFLAGS) $(CPPFLAGS)
+
 # We need libpq only because fe_utils does.
 LDFLAGS_INTERNAL += -L$(top_builddir)/src/fe_utils -lpgfeutils $(libpq_pgport) $(ICU_LIBS)
 
diff --git a/src/bin/initdb/meson.build b/src/bin/initdb/meson.build
index 49743630aa..28a2df99e4 100644
--- a/src/bin/initdb/meson.build
+++ b/src/bin/initdb/meson.build
@@ -7,19 +7,25 @@ initdb_sources = files(
 
 initdb_sources += timezone_localtime_source
 
-#fixme: reimplement libpq_pgport logic
-
 if host_system == 'windows'
   initdb_sources += rc_bin_gen.process(win32ver_rc, extra_args: [
     '--NAME', 'initdb',
     '--FILEDESC', 'initdb - initialize a new database cluster',])
 endif
 
+# Note: it's important that we link to encnames.o from libpgcommon, not
+# from libpq, else we have risks of version skew if we run with a libpq
+# shared library from a different PG version.  Define
+# USE_PRIVATE_ENCODING_FUNCS to ensure that that happens.
+c_args = default_bin_args.get('c_args', []) + ['-DUSE_PRIVATE_ENCODING_FUNCS']
+
 initdb = executable('initdb',
   initdb_sources,
   include_directories: [timezone_inc],
   dependencies: [frontend_code, libpq, icu, icu_i18n],
-  kwargs: default_bin_args,
+  kwargs: default_bin_args + {
+    'c_args': c_args,
+  },
 )
 bin_targets += initdb
 
diff --git a/src/common/Makefile b/src/common/Makefile
index cc5c54dcee..70884be00c 100644
--- a/src/common/Makefile
+++ b/src/common/Makefile
@@ -140,6 +140,13 @@ libpgcommon.a: $(OBJS_FRONTEND)
 	rm -f $@
 	$(AR) $(AROPT) $@ $^
 
+#
+# Files in libpgcommon.a should use/export the "xxx_private" versions
+# of pg_char_to_encoding() and friends.
+#
+$(OBJS_FRONTEND): CPPFLAGS += -DUSE_PRIVATE_ENCODING_FUNCS
+
+
 #
 # Shared library versions of object files
 #
diff --git a/src/common/meson.build b/src/common/meson.build
index 3b97497d1a..ae05ac63cf 100644
--- a/src/common/meson.build
+++ b/src/common/meson.build
@@ -112,8 +112,8 @@ common_sources_frontend_static += files(
   'logging.c',
 )
 
-# Build pgport once for backend, once for use in frontend binaries, and once
-# for use in shared libraries
+# Build pgcommon once for backend, once for use in frontend binaries, and
+# once for use in shared libraries
 #
 # XXX: in most environments we could probably link_whole pgcommon_shlib
 # against pgcommon_static, instead of compiling twice.
@@ -131,6 +131,9 @@ pgcommon_variants = {
   '': default_lib_args + {
     'sources': common_sources_frontend_static,
     'dependencies': [frontend_common_code],
+    # Files in libpgcommon.a should use/export the "xxx_private" versions
+    # of pg_char_to_encoding() and friends.
+    'c_args': ['-DUSE_PRIVATE_ENCODING_FUNCS'],
   },
   '_shlib': default_lib_args + {
     'pic': true,
diff --git a/src/include/mb/pg_wchar.h b/src/include/mb/pg_wchar.h
index 25276b199f..29cd5732f1 100644
--- a/src/include/mb/pg_wchar.h
+++ b/src/include/mb/pg_wchar.h
@@ -13,6 +13,9 @@
  *		included by libpq client programs.  In particular, a libpq client
  *		should not assume that the encoding IDs used by the version of libpq
  *		it's linked to match up with the IDs declared here.
+ *		To help prevent mistakes, relevant functions that are exported by
+ *		libpq have a physically different name when being referenced
+ *		statically.
  *
  *-------------------------------------------------------------------------
  */
@@ -562,6 +565,23 @@ surrogate_pair_to_codepoint(pg_wchar first, pg_wchar second)
 }
 
 
+/*
+ * The functions in this list are exported by libpq, and we need to be sure
+ * that we know which calls are satisfied by libpq and which are satisfied
+ * by static linkage to libpgcommon.  (This is because we might be using a
+ * libpq.so that's of a different major version and has encoding IDs that
+ * differ from the current version's.)  The nominal function names are what
+ * are actually used in and exported by libpq, while the names exported by
+ * libpgcommon.a and libpgcommon_srv.a end in "_private".
+ */
+#if defined(USE_PRIVATE_ENCODING_FUNCS) || !defined(FRONTEND)
+#define pg_char_to_encoding			pg_char_to_encoding_private
+#define pg_encoding_to_char			pg_encoding_to_char_private
+#define pg_valid_server_encoding	pg_valid_server_encoding_private
+#define pg_valid_server_encoding_id	pg_valid_server_encoding_id_private
+#define pg_utf_mblen				pg_utf_mblen_private
+#endif
+
 /*
  * These functions are considered part of libpq's exported API and
  * are also declared in libpq-fe.h.