diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index 829613f26c..d8ea2da583 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -451,7 +451,9 @@ echo "+++ tap install-check in $(subdir) +++" && \
 rm -rf '$(CURDIR)'/tmp_check && \
 $(MKDIR_P) '$(CURDIR)'/tmp_check && \
 cd $(srcdir) && \
-   TESTDIR='$(CURDIR)/tmp_check' PATH="$(bindir):$(CURDIR):$$PATH" \
+   TESTLOGDIR='$(CURDIR)/tmp_check/log' \
+   TESTDATADIR='$(CURDIR)/tmp_check' \
+   PATH="$(bindir):$(CURDIR):$$PATH" \
    PGPORT='6$(DEF_PGPORT)' top_builddir='$(CURDIR)/$(top_builddir)' \
    PG_REGRESS='$(CURDIR)/$(top_builddir)/src/test/regress/pg_regress' \
    $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
@@ -462,7 +464,9 @@ echo "+++ tap install-check in $(subdir) +++" && \
 rm -rf '$(CURDIR)'/tmp_check && \
 $(MKDIR_P) '$(CURDIR)'/tmp_check && \
 cd $(srcdir) && \
-   TESTDIR='$(CURDIR)/tmp_check' PATH="$(bindir):$(CURDIR):$$PATH" \
+   TESTLOGDIR='$(CURDIR)/tmp_check/log' \
+   TESTDATADIR='$(CURDIR)/tmp_check' \
+   PATH="$(bindir):$(CURDIR):$$PATH" \
    PGPORT='6$(DEF_PGPORT)' top_builddir='$(top_builddir)' \
    PG_REGRESS='$(top_builddir)/src/test/regress/pg_regress' \
    $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
@@ -474,7 +478,10 @@ echo "+++ tap check in $(subdir) +++" && \
 rm -rf '$(CURDIR)'/tmp_check && \
 $(MKDIR_P) '$(CURDIR)'/tmp_check && \
 cd $(srcdir) && \
-   TESTDIR='$(CURDIR)/tmp_check' $(with_temp_install) PGPORT='6$(DEF_PGPORT)' \
+   TESTLOGDIR='$(CURDIR)/tmp_check/log' \
+   TESTDATADIR='$(CURDIR)/tmp_check' \
+   $(with_temp_install) \
+   PGPORT='6$(DEF_PGPORT)' \
    PG_REGRESS='$(CURDIR)/$(top_builddir)/src/test/regress/pg_regress' \
    $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
 endef
diff --git a/src/bin/psql/t/010_tab_completion.pl b/src/bin/psql/t/010_tab_completion.pl
index cb36e8e481..4aa6dd5fe1 100644
--- a/src/bin/psql/t/010_tab_completion.pl
+++ b/src/bin/psql/t/010_tab_completion.pl
@@ -70,9 +70,9 @@ delete $ENV{LS_COLORS};
 # to run in the build directory so that we can use relative paths to
 # access the tab_comp_dir subdirectory; otherwise the output from filename
 # completion tests is too variable.
-if ($ENV{TESTDIR})
+if ($ENV{TESTDATADIR})
 {
-	chdir $ENV{TESTDIR} or die "could not chdir to \"$ENV{TESTDIR}\": $!";
+	chdir $ENV{TESTDATADIR} or die "could not chdir to \"$ENV{TESTDATADIR}\": $!";
 }
 
 # Create some junk files for filename completion testing.
diff --git a/src/test/perl/PostgreSQL/Test/Utils.pm b/src/test/perl/PostgreSQL/Test/Utils.pm
index 88a472f244..99d3345106 100644
--- a/src/test/perl/PostgreSQL/Test/Utils.pm
+++ b/src/test/perl/PostgreSQL/Test/Utils.pm
@@ -189,11 +189,11 @@ INIT
 	# test may still fail, but it's more likely to report useful facts.
 	$SIG{PIPE} = 'IGNORE';
 
-	# Determine output directories, and create them.  The base path is the
-	# TESTDIR environment variable, which is normally set by the invoking
-	# Makefile.
-	$tmp_check = $ENV{TESTDIR} ? "$ENV{TESTDIR}" : "tmp_check";
-	$log_path = "$tmp_check/log";
+	# Determine output directories, and create them.  The base paths are the
+	# TESTDATADIR / TESTLOGDIR environment variables, which are normally set
+	# by the invoking Makefile.
+	$tmp_check = $ENV{TESTDATADIR} ? "$ENV{TESTDATADIR}" : "tmp_check";
+	$log_path = $ENV{TESTLOGDIR} ? "$ENV{TESTLOGDIR}" : "log";
 
 	mkdir $tmp_check;
 	mkdir $log_path;
diff --git a/src/tools/msvc/vcregress.pl b/src/tools/msvc/vcregress.pl
index da152da8e5..5182721eb7 100644
--- a/src/tools/msvc/vcregress.pl
+++ b/src/tools/msvc/vcregress.pl
@@ -291,7 +291,9 @@ sub tap_check
 	$ENV{PG_REGRESS}    = "$topdir/$Config/pg_regress/pg_regress";
 	$ENV{REGRESS_SHLIB} = "$topdir/src/test/regress/regress.dll";
 
-	$ENV{TESTDIR} = "$dir/tmp_check";
+	$ENV{TESTDATADIR} = "$dir/tmp_check";
+	$ENV{TESTLOGDIR} = "$dir/tmp_check/log";
+
 	my $module = basename $dir;
 	# add the module build dir as the second element in the PATH
 	$ENV{PATH} =~ s!;!;$topdir/$Config/$module;!;