diff --git a/src/python/scalapb/pants/register.py b/src/python/scalapb/pants/register.py
index 33bec75..ad438a7 100644
--- a/src/python/scalapb/pants/register.py
+++ b/src/python/scalapb/pants/register.py
@@ -1,14 +1,18 @@
 from pants.build_graph.build_file_aliases import BuildFileAliases
 from scalapb.pants.targets.scalapb_library import ScalaPBLibrary
+from scalapb.pants.targets.target_types import ScalaPBLibraryTarget
 from scalapb.pants.tasks.scalapb_gen import ScalaPBGen
 from pants.goal.task_registrar import TaskRegistrar as task
 
 def build_file_aliases():
     return BuildFileAliases(
         targets={
-          'scalapb_library': ScalaPBLibrary,
+            ScalaPBLibrary.alias(): ScalaPBLibrary,
         }
     )
 
 def register_goals():
     task(name='scalapb-gen', action=ScalaPBGen).install('gen')
+
+def target_types():
+    return [ScalaPBLibraryTarget]
diff --git a/src/python/scalapb/pants/targets/scalapb_library.py b/src/python/scalapb/pants/targets/scalapb_library.py
index 5cbe753..02aa3aa 100644
--- a/src/python/scalapb/pants/targets/scalapb_library.py
+++ b/src/python/scalapb/pants/targets/scalapb_library.py
@@ -1,18 +1,12 @@
 from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
                         unicode_literals, with_statement)
 
-import logging
-
 from pants.backend.jvm.targets.import_jars_mixin import ImportJarsMixin
 from pants.backend.jvm.targets.jvm_target import JvmTarget
 from pants.base.payload import Payload
 from pants.base.payload_field import PrimitiveField
-
 import os
 
-
-logger = logging.getLogger(__name__)
-
 class ScalaPBLibrary(ImportJarsMixin, JvmTarget):
   """A Java library generated from Protocol Buffer IDL files."""
 
@@ -39,6 +33,10 @@ def __init__(self,
     })
     super(ScalaPBLibrary, self).__init__(payload=payload, **kwargs)
 
+  @classmethod
+  def alias(cls):
+    return "scalapb_library"
+
   @property
   def source_root(self):
     return os.path.normpath(
diff --git a/src/python/scalapb/pants/targets/target_types.py b/src/python/scalapb/pants/targets/target_types.py
new file mode 100644
index 0000000..599fe0a
--- /dev/null
+++ b/src/python/scalapb/pants/targets/target_types.py
@@ -0,0 +1,34 @@
+from pants.engine.target import (
+    COMMON_TARGET_FIELDS,
+    Dependencies,
+    Sources,
+    StringField,
+    StringSequenceField,
+    Target,
+)
+
+from pants.backend.jvm.target_types import (
+  COMMON_JVM_FIELDS,
+)
+
+class Imports(StringSequenceField):
+    alias = "imports"
+
+class SourceRoot(StringField):
+    alias = "source_root"
+
+class ProtobufSources(Sources):
+    default = ("*.proto",)
+    expected_file_extensions = (".proto",)
+
+class ScalaPBLibraryTarget(Target):
+    """A Scala library generated from Protobuf IDL files."""
+
+    alias = "scalapb_library"
+    core_fields = (
+        *COMMON_JVM_FIELDS,
+       Imports,
+       SourceRoot,
+       ProtobufSources
+    )
+    v1_only = True
diff --git a/src/python/scalapb/pants/tasks/scalapb_gen.py b/src/python/scalapb/pants/tasks/scalapb_gen.py
index 36893b3..ed64be4 100644
--- a/src/python/scalapb/pants/tasks/scalapb_gen.py
+++ b/src/python/scalapb/pants/tasks/scalapb_gen.py
@@ -35,7 +35,7 @@ def register_options(cls, register):
     super(ScalaPBGen, cls).register_options(register)
     cls.register_jvm_tool(register, 'scalapbc')
     register('--protoc-version', fingerprint=True,
-             help='Set a specific protoc version to use.', default='330')
+             help='Set a specific protoc version to use.', default='3.3.0')
 
   def synthetic_target_type(self, target):
     return ScalaLibrary
@@ -48,6 +48,8 @@ def execute_codegen(self, target, target_workdir):
 
     source_roots = self._calculate_source_roots(target)
     source_roots.update(self._proto_path_imports([target]))
+    # This is needed when used with unpacked jars
+    source_roots.add(target._sources_field.sources.rel_root)
 
     scalapb_options = []
     if target.payload.java_conversions:
@@ -69,7 +71,8 @@ def execute_codegen(self, target, target_workdir):
     source_roots = list(source_roots)
     source_roots.sort()
     for source_root in source_roots:
-      args.append('--proto_path={0}'.format(source_root))
+      if (source_root != '.'):
+        args.append('--proto_path={0}'.format(source_root))
 
     classpath = self.tool_classpath('scalapbc')