diff --git a/README.rst b/README.rst
index f84f304ad..69c790daf 100644
--- a/README.rst
+++ b/README.rst
@@ -300,9 +300,13 @@ a constraint:
     django-debug-toolbar==2.2
         # via -r dev-requirements.in
     django==2.1.15
-        # via -c requirements.txt, django-debug-toolbar
+        # via
+        #   -c requirements.txt
+        #   django-debug-toolbar
     pytz==2019.3
-        # via -c requirements.txt, django
+        # via
+        #   -c requirements.txt
+        #   django
     sqlparse==0.3.0
         # via django-debug-toolbar
 
diff --git a/piptools/writer.py b/piptools/writer.py
index 23d3445fa..515df198e 100644
--- a/piptools/writer.py
+++ b/piptools/writer.py
@@ -230,6 +230,14 @@ def _format_requirement(self, ireq, marker=None, hashes=None):
         elif ireq.comes_from:
             required_by.add(_comes_from_as_string(ireq))
         if required_by:
-            annotation = ", ".join(sorted(required_by))
-            line = "{}\n    {}".format(line, comment("# via " + annotation))
+            required_by = sorted(required_by)
+            if len(required_by) == 1:
+                source = required_by[0]
+                annotation = "    # via " + source
+            else:
+                annotation_lines = ["    # via"]
+                for source in required_by:
+                    annotation_lines.append("    #   " + source)
+                annotation = "\n".join(annotation_lines)
+            line = "{}\n{}".format(line, comment(annotation))
         return line
diff --git a/tests/test_cli_compile.py b/tests/test_cli_compile.py
index f59774bd3..cca7ecbd6 100644
--- a/tests/test_cli_compile.py
+++ b/tests/test_cli_compile.py
@@ -768,6 +768,61 @@ def test_generate_hashes_with_annotations(runner):
     )
 
 
+@pytest.mark.network
+def test_generate_hashes_with_long_annotations(runner):
+    with open("requirements.in", "w") as fp:
+        fp.write("django-debug-toolbar==1.11\n")
+        fp.write("django-storages==1.9.1\n")
+        fp.write("django-taggit==0.24.0\n")
+        fp.write("Django==1.11.29\n")
+        fp.write("pytz==2020.4\n")
+        fp.write("sqlparse==0.3.1\n")
+
+    out = runner.invoke(cli, ["--generate-hashes"])
+    assert out.stderr == dedent(
+        """\
+        #
+        # This file is autogenerated by pip-compile
+        # To update, run:
+        #
+        #    pip-compile --generate-hashes
+        #
+        django-debug-toolbar==1.11 \\
+            --hash=sha256:89d75b60c65db363fb24688d977e5fbf0e73386c67acf562d278402a10fc3736 \\
+            --hash=sha256:c2b0134119a624f4ac9398b44f8e28a01c7686ac350a12a74793f3dd57a9eea0
+            # via -r requirements.in
+        django-storages==1.9.1 \\
+            --hash=sha256:3103991c2ee8cef8a2ff096709973ffe7106183d211a79f22cf855f33533d924 \\
+            --hash=sha256:a59e9923cbce7068792f75344ed7727021ee4ac20f227cf17297d0d03d141e91
+            # via -r requirements.in
+        django-taggit==0.24.0 \\
+            --hash=sha256:710b4d15ec1996550cc68a0abbc41903ca7d832540e52b1336e6858737e410d8 \\
+            --hash=sha256:bb8f27684814cd1414b2af75b857b5e26a40912631904038a7ecacd2bfafc3ac
+            # via -r requirements.in
+        django==1.11.29 \\
+            --hash=sha256:014e3392058d94f40569206a24523ce254d55ad2f9f46c6550b0fe2e4f94cf3f \\
+            --hash=sha256:4200aefb6678019a0acf0005cd14cfce3a5e6b9b90d06145fcdd2e474ad4329c
+            # via
+            #   -r requirements.in
+            #   django-debug-toolbar
+            #   django-storages
+            #   django-taggit
+        pytz==2020.4 \\
+            --hash=sha256:3e6b7dd2d1e0a59084bcee14a17af60c5c562cdc16d828e8eba2e683d3a7e268 \\
+            --hash=sha256:5c55e189b682d420be27c6995ba6edce0c0a77dd67bfbe2ae6607134d5851ffd
+            # via
+            #   -r requirements.in
+            #   django
+        sqlparse==0.3.1 \\
+            --hash=sha256:022fb9c87b524d1f7862b3037e541f68597a730a8843245c349fc93e1643dc4e \\
+            --hash=sha256:e162203737712307dfe78860cc56c8da8a852ab2ee33750e33aeadf38d12c548
+            # via
+            #   -r requirements.in
+            #   django-debug-toolbar
+        """
+    )
+
+
 def test_filter_pip_markers(pip_conf, runner):
     """
     Check that pip-compile works with pip environment markers (PEP496)
@@ -911,7 +966,9 @@ def test_multiple_input_files_without_output_file(runner):
             #    pip-compile --no-emit-find-links
             #
             small-fake-a==0.1
-                # via -c constraints.txt, small-fake-with-deps
+                # via
+                #   -c constraints.txt
+                #   small-fake-with-deps
             small-fake-with-deps==0.1
                 # via -r requirements.in
             Dry-run, so nothing updated.
diff --git a/tests/test_writer.py b/tests/test_writer.py
index 2811c4eba..4abbdffcb 100644
--- a/tests/test_writer.py
+++ b/tests/test_writer.py
@@ -53,21 +53,21 @@ def test_format_requirement_annotation_editable(from_editable, writer):
 
     assert writer._format_requirement(
         ireq
-    ) == "-e git+git://fake.org/x/y.git#egg=y\n    " + comment("# via xyz")
+    ) == "-e git+git://fake.org/x/y.git#egg=y\n" + comment("    # via xyz")
 
 
 def test_format_requirement_annotation(from_line, writer):
     ireq = from_line("test==1.2")
     ireq.comes_from = "xyz"
 
-    assert writer._format_requirement(ireq) == "test==1.2\n    " + comment("# via xyz")
+    assert writer._format_requirement(ireq) == "test==1.2\n" + comment("    # via xyz")
 
 
 def test_format_requirement_annotation_lower_case(from_line, writer):
     ireq = from_line("Test==1.2")
     ireq.comes_from = "xyz"
 
-    assert writer._format_requirement(ireq) == "test==1.2\n    " + comment("# via xyz")
+    assert writer._format_requirement(ireq) == "test==1.2\n" + comment("    # via xyz")
 
 
 def test_format_requirement_for_primary(from_line, writer):
@@ -75,7 +75,7 @@ def test_format_requirement_for_primary(from_line, writer):
     ireq = from_line("test==1.2")
     ireq.comes_from = "xyz"
 
-    assert writer._format_requirement(ireq) == "test==1.2\n    " + comment("# via xyz")
+    assert writer._format_requirement(ireq) == "test==1.2\n" + comment("    # via xyz")
 
 
 def test_format_requirement_for_primary_lower_case(from_line, writer):
@@ -83,7 +83,7 @@ def test_format_requirement_for_primary_lower_case(from_line, writer):
     ireq = from_line("Test==1.2")
     ireq.comes_from = "xyz"
 
-    assert writer._format_requirement(ireq) == "test==1.2\n    " + comment("# via xyz")
+    assert writer._format_requirement(ireq) == "test==1.2\n" + comment("    # via xyz")
 
 
 def test_format_requirement_environment_marker(from_line, writer):