diff --git a/t/t5500-fetch-pack.sh b/t/t5500-fetch-pack.sh
index 086f2c40f6..8b1217ea26 100755
--- a/t/t5500-fetch-pack.sh
+++ b/t/t5500-fetch-pack.sh
@@ -628,7 +628,10 @@ test_expect_success 'fetch-pack cannot fetch a raw sha1 that is not advertised a
 	test_commit -C server 6 &&
 
 	git init client &&
-	test_must_fail git -C client fetch-pack ../server \
+
+	# Other protocol versions (e.g. 2) allow fetching an unadvertised
+	# object, so run this test with the default protocol version (0).
+	test_must_fail env GIT_TEST_PROTOCOL_VERSION= git -C client fetch-pack ../server \
 		$(git -C server rev-parse refs/heads/master^) 2>err &&
 	test_i18ngrep "Server does not allow request for unadvertised object" err
 '
@@ -788,7 +791,7 @@ test_expect_success 'shallow clone exclude tag two' '
 '
 
 test_expect_success 'fetch exclude tag one' '
-	git -C shallow12 fetch --shallow-exclude one origin &&
+	GIT_TEST_PROTOCOL_VERSION= git -C shallow12 fetch --shallow-exclude one origin &&
 	git -C shallow12 log --pretty=tformat:%s origin/master >actual &&
 	test_write_lines three two >expected &&
 	test_cmp expected actual
@@ -806,7 +809,7 @@ test_expect_success 'fetching deepen' '
 	git -C deepen log --pretty=tformat:%s master >actual &&
 	echo three >expected &&
 	test_cmp expected actual &&
-	git -C deepen fetch --deepen=1 &&
+	GIT_TEST_PROTOCOL_VERSION= git -C deepen fetch --deepen=1 &&
 	git -C deepen log --pretty=tformat:%s origin/master >actual &&
 	cat >expected <<-\EOF &&
 	four
diff --git a/t/t5503-tagfollow.sh b/t/t5503-tagfollow.sh
index 4ca48f0276..0e90a90294 100755
--- a/t/t5503-tagfollow.sh
+++ b/t/t5503-tagfollow.sh
@@ -56,7 +56,7 @@ test_expect_success 'fetch A (new commit : 1 connection)' '
 	rm -f $U &&
 	(
 		cd cloned &&
-		GIT_TRACE_PACKET=$UPATH git fetch &&
+		GIT_TRACE_PACKET=$UPATH GIT_TEST_PROTOCOL_VERSION= git fetch &&
 		test $A = $(git rev-parse --verify origin/master)
 	) &&
 	get_needs $U >actual &&
@@ -86,7 +86,7 @@ test_expect_success 'fetch C, T (new branch, tag : 1 connection)' '
 	rm -f $U &&
 	(
 		cd cloned &&
-		GIT_TRACE_PACKET=$UPATH git fetch &&
+		GIT_TRACE_PACKET=$UPATH GIT_TEST_PROTOCOL_VERSION= git fetch &&
 		test $C = $(git rev-parse --verify origin/cat) &&
 		test $T = $(git rev-parse --verify tag1) &&
 		test $A = $(git rev-parse --verify tag1^0)
@@ -122,7 +122,7 @@ test_expect_success 'fetch B, S (commit and tag : 1 connection)' '
 	rm -f $U &&
 	(
 		cd cloned &&
-		GIT_TRACE_PACKET=$UPATH git fetch &&
+		GIT_TRACE_PACKET=$UPATH GIT_TEST_PROTOCOL_VERSION= git fetch &&
 		test $B = $(git rev-parse --verify origin/master) &&
 		test $B = $(git rev-parse --verify tag2^0) &&
 		test $S = $(git rev-parse --verify tag2)
@@ -146,7 +146,7 @@ test_expect_success 'new clone fetch master and tags' '
 		cd clone2 &&
 		git init &&
 		git remote add origin .. &&
-		GIT_TRACE_PACKET=$UPATH git fetch &&
+		GIT_TRACE_PACKET=$UPATH GIT_TEST_PROTOCOL_VERSION= git fetch &&
 		test $B = $(git rev-parse --verify origin/master) &&
 		test $S = $(git rev-parse --verify tag2) &&
 		test $B = $(git rev-parse --verify tag2^0) &&
diff --git a/t/t5512-ls-remote.sh b/t/t5512-ls-remote.sh
index ca69636fd5..7b480587c9 100755
--- a/t/t5512-ls-remote.sh
+++ b/t/t5512-ls-remote.sh
@@ -223,7 +223,7 @@ test_expect_success 'ls-remote --symref' '
 	$(git rev-parse refs/tags/mark1.10)	refs/tags/mark1.10
 	$(git rev-parse refs/tags/mark1.2)	refs/tags/mark1.2
 	EOF
-	git ls-remote --symref >actual &&
+	GIT_TEST_PROTOCOL_VERSION= git ls-remote --symref >actual &&
 	test_cmp expect actual
 '
 
@@ -243,7 +243,7 @@ test_expect_failure 'ls-remote with filtered symref (--heads)' '
 	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/foo
 	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/master
 	EOF
-	git ls-remote --symref --heads . >actual &&
+	GIT_TEST_PROTOCOL_VERSION= git ls-remote --symref --heads . >actual &&
 	test_cmp expect actual
 '
 
@@ -252,9 +252,9 @@ test_expect_success 'ls-remote --symref omits filtered-out matches' '
 	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/foo
 	1bd44cb9d13204b0fe1958db0082f5028a16eb3a	refs/heads/master
 	EOF
-	git ls-remote --symref --heads . >actual &&
+	GIT_TEST_PROTOCOL_VERSION=  git ls-remote --symref --heads . >actual &&
 	test_cmp expect actual &&
-	git ls-remote --symref . "refs/heads/*" >actual &&
+	GIT_TEST_PROTOCOL_VERSION= git ls-remote --symref . "refs/heads/*" >actual &&
 	test_cmp expect actual
 '
 
diff --git a/t/t5515-fetch-merge-logic.sh b/t/t5515-fetch-merge-logic.sh
index 36b0dbc01c..f095555c3e 100755
--- a/t/t5515-fetch-merge-logic.sh
+++ b/t/t5515-fetch-merge-logic.sh
@@ -147,7 +147,7 @@ do
 			do
 				git update-ref -d "$refname" "$val"
 			done
-			git fetch "$@" >/dev/null
+			GIT_TEST_PROTOCOL_VERSION= git fetch "$@" >/dev/null
 			cat .git/FETCH_HEAD
 		} >"$actual_f" &&
 		git show-ref >"$actual_r" &&
diff --git a/t/t5516-fetch-push.sh b/t/t5516-fetch-push.sh
index 08cdee0b95..1d1b717cd5 100755
--- a/t/t5516-fetch-push.sh
+++ b/t/t5516-fetch-push.sh
@@ -1129,7 +1129,7 @@ do
 	'
 done
 
-test_expect_success 'fetch exact SHA1' '
+test_expect_success 'fetch exact SHA1 in protocol v0' '
 	mk_test testrepo heads/master hidden/one &&
 	git push testrepo master:refs/hidden/one &&
 	(
@@ -1148,7 +1148,8 @@ test_expect_success 'fetch exact SHA1' '
 		test_must_fail git cat-file -t $the_commit &&
 
 		# fetching the hidden object should fail by default
-		test_must_fail git fetch -v ../testrepo $the_commit:refs/heads/copy 2>err &&
+		test_must_fail env GIT_TEST_PROTOCOL_VERSION= \
+			git fetch -v ../testrepo $the_commit:refs/heads/copy 2>err &&
 		test_i18ngrep "Server does not allow request for unadvertised object" err &&
 		test_must_fail git rev-parse --verify refs/heads/copy &&
 
@@ -1205,7 +1206,8 @@ do
 		mk_empty shallow &&
 		(
 			cd shallow &&
-			test_must_fail git fetch --depth=1 ../testrepo/.git $SHA1 &&
+			test_must_fail env GIT_TEST_PROTOCOL_VERSION= \
+				git fetch --depth=1 ../testrepo/.git $SHA1 &&
 			git --git-dir=../testrepo/.git config uploadpack.allowreachablesha1inwant true &&
 			git fetch --depth=1 ../testrepo/.git $SHA1 &&
 			git cat-file commit $SHA1
@@ -1233,15 +1235,18 @@ do
 		mk_empty shallow &&
 		(
 			cd shallow &&
-			test_must_fail ok=sigpipe git fetch ../testrepo/.git $SHA1_3 &&
-			test_must_fail ok=sigpipe git fetch ../testrepo/.git $SHA1_1 &&
+			test_must_fail ok=sigpipe env GIT_TEST_PROTOCOL_VERSION= \
+				git fetch ../testrepo/.git $SHA1_3 &&
+			test_must_fail ok=sigpipe env GIT_TEST_PROTOCOL_VERSION= \
+				git fetch ../testrepo/.git $SHA1_1 &&
 			git --git-dir=../testrepo/.git config uploadpack.allowreachablesha1inwant true &&
 			git fetch ../testrepo/.git $SHA1_1 &&
 			git cat-file commit $SHA1_1 &&
 			test_must_fail git cat-file commit $SHA1_2 &&
 			git fetch ../testrepo/.git $SHA1_2 &&
 			git cat-file commit $SHA1_2 &&
-			test_must_fail ok=sigpipe git fetch ../testrepo/.git $SHA1_3
+			test_must_fail ok=sigpipe env GIT_TEST_PROTOCOL_VERSION= \
+				git fetch ../testrepo/.git $SHA1_3
 		)
 	'
 done
diff --git a/t/t5537-fetch-shallow.sh b/t/t5537-fetch-shallow.sh
index 6faf17e17a..85b3022ce6 100755
--- a/t/t5537-fetch-shallow.sh
+++ b/t/t5537-fetch-shallow.sh
@@ -127,7 +127,8 @@ test_expect_success 'fetch that requires changes in .git/shallow is filtered' '
 	git init notshallow &&
 	(
 	cd notshallow &&
-	git fetch ../shallow/.git refs/heads/*:refs/remotes/shallow/*&&
+	GIT_TEST_PROTOCOL_VERSION= \
+		git fetch ../shallow/.git refs/heads/*:refs/remotes/shallow/* &&
 	git for-each-ref --format="%(refname)" >actual.refs &&
 	cat <<EOF >expect.refs &&
 refs/remotes/shallow/no-shallow
diff --git a/t/t5539-fetch-http-shallow.sh b/t/t5539-fetch-http-shallow.sh
index 5fbf67c446..a121e19bc7 100755
--- a/t/t5539-fetch-http-shallow.sh
+++ b/t/t5539-fetch-http-shallow.sh
@@ -67,7 +67,8 @@ test_expect_success 'no shallow lines after receiving ACK ready' '
 		cd clone &&
 		git checkout --orphan newnew &&
 		test_commit new-too &&
-		GIT_TRACE_PACKET="$TRASH_DIRECTORY/trace" git fetch --depth=2 &&
+		GIT_TRACE_PACKET="$TRASH_DIRECTORY/trace" GIT_TEST_PROTOCOL_VERSION= \
+			git fetch --depth=2 &&
 		grep "fetch-pack< ACK .* ready" ../trace &&
 		! grep "fetch-pack> done" ../trace
 	)
@@ -114,7 +115,7 @@ test_expect_success 'shallow clone exclude tag two' '
 '
 
 test_expect_success 'fetch exclude tag one' '
-	git -C shallow12 fetch --shallow-exclude one origin &&
+	GIT_TEST_PROTOCOL_VERSION= git -C shallow12 fetch --shallow-exclude one origin &&
 	git -C shallow12 log --pretty=tformat:%s origin/master >actual &&
 	test_write_lines three two >expected &&
 	test_cmp expected actual
@@ -128,14 +129,14 @@ test_expect_success 'fetching deepen' '
 	test_commit two &&
 	test_commit three &&
 	mv .git "$HTTPD_DOCUMENT_ROOT_PATH/shallow-deepen.git" &&
-	git clone --depth 1 $HTTPD_URL/smart/shallow-deepen.git deepen &&
+	GIT_TEST_PROTOCOL_VERSION= git clone --depth 1 $HTTPD_URL/smart/shallow-deepen.git deepen &&
 	mv "$HTTPD_DOCUMENT_ROOT_PATH/shallow-deepen.git" .git &&
 	test_commit four &&
 	git -C deepen log --pretty=tformat:%s master >actual &&
 	echo three >expected &&
 	test_cmp expected actual &&
 	mv .git "$HTTPD_DOCUMENT_ROOT_PATH/shallow-deepen.git" &&
-	git -C deepen fetch --deepen=1 &&
+	GIT_TEST_PROTOCOL_VERSION= git -C deepen fetch --deepen=1 &&
 	git -C deepen log --pretty=tformat:%s origin/master >actual &&
 	cat >expected <<-\EOF &&
 	four
diff --git a/t/t5541-http-push-smart.sh b/t/t5541-http-push-smart.sh
index 5475afc052..180c9005b7 100755
--- a/t/t5541-http-push-smart.sh
+++ b/t/t5541-http-push-smart.sh
@@ -45,14 +45,19 @@ test_expect_success 'no empty path components' '
 	# In the URL, add a trailing slash, and see if git appends yet another
 	# slash.
 	cd "$ROOT_PATH" &&
-	git clone $HTTPD_URL/smart/test_repo.git/ test_repo_clone &&
+	# Other protocol versions may make different requests, so perform this
+	# clone with the default protocol.
+	GIT_TEST_PROTOCOL_VERSION= git clone $HTTPD_URL/smart/test_repo.git/ test_repo_clone &&
 
 	check_access_log exp
 '
 
 test_expect_success 'clone remote repository' '
 	rm -rf test_repo_clone &&
-	git clone $HTTPD_URL/smart/test_repo.git test_repo_clone &&
+	# Other protocol versions may make different requests, so perform this
+	# clone with the default protocol.
+	GIT_TEST_PROTOCOL_VERSION= git clone $HTTPD_URL/smart/test_repo.git test_repo_clone &&
+
 	(
 		cd test_repo_clone && git config push.default matching
 	)
diff --git a/t/t5551-http-fetch-smart.sh b/t/t5551-http-fetch-smart.sh
index 8630b0cc39..a51993f35a 100755
--- a/t/t5551-http-fetch-smart.sh
+++ b/t/t5551-http-fetch-smart.sh
@@ -43,7 +43,8 @@ test_expect_success 'clone http repository' '
 	< Cache-Control: no-cache, max-age=0, must-revalidate
 	< Content-Type: application/x-git-upload-pack-result
 	EOF
-	GIT_TRACE_CURL=true git clone --quiet $HTTPD_URL/smart/repo.git clone 2>err &&
+	GIT_TRACE_CURL=true GIT_TEST_PROTOCOL_VERSION= \
+		git clone --quiet $HTTPD_URL/smart/repo.git clone 2>err &&
 	test_cmp file clone/file &&
 	tr '\''\015'\'' Q <err |
 	sed -e "
@@ -92,7 +93,7 @@ test_expect_success 'fetch changes via http' '
 	echo content >>file &&
 	git commit -a -m two &&
 	git push public &&
-	(cd clone && git pull) &&
+	(cd clone && GIT_TEST_PROTOCOL_VERSION= git pull) &&
 	test_cmp file clone/file
 '
 
@@ -143,7 +144,7 @@ test_expect_success 'clone from auth-only-for-push repository' '
 test_expect_success 'clone from auth-only-for-objects repository' '
 	echo two >expect &&
 	set_askpass user@host pass@host &&
-	git clone --bare "$HTTPD_URL/auth-fetch/smart/repo.git" half-auth &&
+	GIT_TEST_PROTOCOL_VERSION= git clone --bare "$HTTPD_URL/auth-fetch/smart/repo.git" half-auth &&
 	expect_askpass both user@host &&
 	git --git-dir=half-auth log -1 --format=%s >actual &&
 	test_cmp expect actual
@@ -151,7 +152,7 @@ test_expect_success 'clone from auth-only-for-objects repository' '
 
 test_expect_success 'no-op half-auth fetch does not require a password' '
 	set_askpass wrong &&
-	git --git-dir=half-auth fetch &&
+	GIT_TEST_PROTOCOL_VERSION= git --git-dir=half-auth fetch &&
 	expect_askpass none
 '
 
@@ -187,7 +188,7 @@ test_expect_success 'create namespaced refs' '
 '
 
 test_expect_success 'smart clone respects namespace' '
-	git clone "$HTTPD_URL/smart_namespace/repo.git" ns-smart &&
+	GIT_TEST_PROTOCOL_VERSION= git clone "$HTTPD_URL/smart_namespace/repo.git" ns-smart &&
 	echo namespaced >expect &&
 	git --git-dir=ns-smart/.git log -1 --format=%s >actual &&
 	test_cmp expect actual
@@ -214,7 +215,7 @@ test_expect_success 'cookies stored in http.cookiefile when http.savecookies set
 	EOF
 	git config http.cookiefile cookies.txt &&
 	git config http.savecookies true &&
-	git ls-remote $HTTPD_URL/smart_cookies/repo.git master &&
+	GIT_TEST_PROTOCOL_VERSION= git ls-remote $HTTPD_URL/smart_cookies/repo.git master &&
 	tail -3 cookies.txt | sort >cookies_tail.txt &&
 	test_cmp expect_cookies.txt cookies_tail.txt
 '
@@ -306,7 +307,8 @@ test_expect_success 'test allowreachablesha1inwant with unreachable' '
 
 	git init --bare test_reachable.git &&
 	git -C test_reachable.git remote add origin "$HTTPD_URL/smart/repo.git" &&
-	test_must_fail git -C test_reachable.git fetch origin "$(git rev-parse HEAD)"
+	test_must_fail env GIT_TEST_PROTOCOL_VERSION= \
+		git -C test_reachable.git fetch origin "$(git rev-parse HEAD)"
 '
 
 test_expect_success 'test allowanysha1inwant with unreachable' '
@@ -325,7 +327,8 @@ test_expect_success 'test allowanysha1inwant with unreachable' '
 
 	git init --bare test_reachable.git &&
 	git -C test_reachable.git remote add origin "$HTTPD_URL/smart/repo.git" &&
-	test_must_fail git -C test_reachable.git fetch origin "$(git rev-parse HEAD)" &&
+	test_must_fail env GIT_TEST_PROTOCOL_VERSION= \
+		git -C test_reachable.git fetch origin "$(git rev-parse HEAD)" &&
 
 	git -C "$server" config uploadpack.allowanysha1inwant 1 &&
 	git -C test_reachable.git fetch origin "$(git rev-parse HEAD)"
diff --git a/t/t5552-skipping-fetch-negotiator.sh b/t/t5552-skipping-fetch-negotiator.sh
index 30857b84a8..979e6583d4 100755
--- a/t/t5552-skipping-fetch-negotiator.sh
+++ b/t/t5552-skipping-fetch-negotiator.sh
@@ -127,7 +127,7 @@ test_expect_success 'use ref advertisement to filter out commits' '
 	# not need to send any ancestors of "c3", but we still need to send "c3"
 	# itself.
 	test_config -C client fetch.negotiationalgorithm skipping &&
-	trace_fetch client origin to_fetch &&
+	GIT_TEST_PROTOCOL_VERSION= trace_fetch client origin to_fetch &&
 	have_sent c5 c4^ c2side &&
 	have_not_sent c4 c4^^ c4^^^
 '
@@ -189,7 +189,7 @@ test_expect_success 'do not send "have" with ancestors of commits that server AC
 	test_commit -C server commit-on-b1 &&
 
 	test_config -C client fetch.negotiationalgorithm skipping &&
-	trace_fetch client "$(pwd)/server" to_fetch &&
+	GIT_TEST_PROTOCOL_VERSION= trace_fetch client "$(pwd)/server" to_fetch &&
 	grep "  fetch" trace &&
 
 	# fetch-pack sends 2 requests each containing 16 "have" lines before
diff --git a/t/t5570-git-daemon.sh b/t/t5570-git-daemon.sh
index 7466aad111..c42ee245cd 100755
--- a/t/t5570-git-daemon.sh
+++ b/t/t5570-git-daemon.sh
@@ -190,7 +190,7 @@ test_expect_success 'daemon log records all attributes' '
 	EOF
 	>daemon.log &&
 	GIT_OVERRIDE_VIRTUAL_HOST=localhost \
-		git -c protocol.version=1 \
+		GIT_TEST_PROTOCOL_VERSION= git -c protocol.version=1 \
 			ls-remote "$GIT_DAEMON_URL/interp.git" &&
 	grep -i extended.attribute daemon.log | cut -d" " -f2- >actual &&
 	test_cmp expect actual
diff --git a/t/t7406-submodule-update.sh b/t/t7406-submodule-update.sh
index e87164aa8f..a555e38845 100755
--- a/t/t7406-submodule-update.sh
+++ b/t/t7406-submodule-update.sh
@@ -943,7 +943,8 @@ test_expect_success 'submodule update clone shallow submodule outside of depth'
 		cd super3 &&
 		sed -e "s#url = ../#url = file://$pwd/#" <.gitmodules >.gitmodules.tmp &&
 		mv -f .gitmodules.tmp .gitmodules &&
-		test_must_fail git submodule update --init --depth=1 2>actual &&
+		test_must_fail env GIT_TEST_PROTOCOL_VERSION= \
+			git submodule update --init --depth=1 2>actual &&
 		test_i18ngrep "Direct fetching of that commit failed." actual &&
 		git -C ../submodule config uploadpack.allowReachableSHA1InWant true &&
 		git submodule update --init --depth=1 >actual &&
