diff --git a/t/t5539-fetch-http-shallow.sh b/t/t5539-fetch-http-shallow.sh
index 5fbf67c446..996ce060cd 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" env --unset=GIT_TEST_PROTOCOL_VERSION \
+			git fetch --depth=2 &&
 		grep "fetch-pack< ACK .* ready" ../trace &&
 		! grep "fetch-pack> done" ../trace
 	)
@@ -114,7 +115,8 @@ test_expect_success 'shallow clone exclude tag two' '
 '
 
 test_expect_success 'fetch exclude tag one' '
-	git -C shallow12 fetch --shallow-exclude one origin &&
+	env --unset=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 +130,16 @@ 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 &&
+	env --unset=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 "$HTTPD_DOCUMENT_ROOT_PATH/shallow-deepen.git" &&
-	git -C deepen fetch --deepen=1 &&
+	env --unset=GIT_TEST_PROTOCOL_VERSION \
+		git -C deepen fetch --deepen=1 &&
 	git -C deepen log --pretty=tformat:%s origin/master >actual &&
 	cat >expected <<-\EOF &&
 	four
diff --git a/t/t5541-http-push-smart.sh b/t/t5541-http-push-smart.sh
index 5475afc052..20f1308578 100755
--- a/t/t5541-http-push-smart.sh
+++ b/t/t5541-http-push-smart.sh
@@ -45,14 +45,20 @@ test_expect_success 'no empty path components' '
 	# In the URL, add a trailing slash, and see if git appends yet another
 	# slash.
 	cd "$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 protocol v0.
+	env --unset=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 protocol v0.
+	env --unset=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..56fd9351a6 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 env --unset=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 && env --unset=GIT_TEST_PROTOCOL_VERSION git pull) &&
 	test_cmp file clone/file
 '
 
@@ -143,7 +144,8 @@ 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 "$HTTPD_URL/auth-fetch/smart/repo.git" half-auth &&
+	env --unset=GIT_TEST_PROTOCOL_VERSION \
+		git clone --bare "$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 +153,8 @@ 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 &&
+	env --unset=GIT_TEST_PROTOCOL_VERSION \
+		git --git-dir=half-auth fetch &&
 	expect_askpass none
 '
 
@@ -187,7 +190,8 @@ test_expect_success 'create namespaced refs' '
 '
 
 test_expect_success 'smart clone respects namespace' '
-	git clone "$HTTPD_URL/smart_namespace/repo.git" ns-smart &&
+	env --unset=GIT_TEST_PROTOCOL_VERSION \
+		git clone "$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 +218,8 @@ 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 &&
+	env --unset=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 +311,8 @@ 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 --unset=GIT_TEST_PROTOCOL_VERSION \
+		git -C test_reachable.git fetch origin "$(git rev-parse HEAD)"
 '
 
 test_expect_success 'test allowanysha1inwant with unreachable' '
@@ -325,7 +331,8 @@ 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 --unset=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/t5570-git-daemon.sh b/t/t5570-git-daemon.sh
index 7466aad111..4a2a937bb0 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 \
+		env --unset=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
