diff --git a/conda_env/env.py b/conda_env/env.py
index 10d6d3064fd..ab800aaa6a7 100644
--- a/conda_env/env.py
+++ b/conda_env/env.py
@@ -23,6 +23,32 @@
     from conda._vendor.toolz.itertoolz import concatv, groupby  # NOQA
 
 
+VALID_KEYS = ('name', 'dependencies', 'prefix', 'channels')
+
+
+def validate_keys(data, kwargs):
+    """Check for unknown keys, remove them and print a warning."""
+    invalid_keys = []
+    new_data = data.copy()
+    for key in data.keys():
+        if key not in VALID_KEYS:
+            invalid_keys.append(key)
+            new_data.pop(key)
+
+    if invalid_keys:
+        filename = kwargs.get('filename')
+        verb = 'are' if len(invalid_keys) != 1 else 'is'
+        plural = 's' if len(invalid_keys) != 1 else ''
+        print("\nEnvironmentSectionNotValid: The following section{plural} on "
+              "'{filename}' {verb} invalid and will be ignored:"
+              "".format(filename=filename, plural=plural, verb=verb))
+        for key in invalid_keys:
+            print(' - {}'.format(key))
+        print('')
+
+    return new_data
+
+
 def load_from_directory(directory):
     """Load and return an ``Environment`` from a given ``directory``"""
     files = ['environment.yml', 'environment.yaml']
@@ -86,9 +112,12 @@ def from_environment(name, prefix, no_builds=False, ignore_channels=False):
 def from_yaml(yamlstr, **kwargs):
     """Load and return a ``Environment`` from a given ``yaml string``"""
     data = yaml_load_standard(yamlstr)
+    data = validate_keys(data, kwargs)
+
     if kwargs is not None:
         for key, value in kwargs.items():
             data[key] = value
+
     return Environment(**data)
 
 
diff --git a/conda_env/exceptions.py b/conda_env/exceptions.py
index 1b6e95e1684..d8bc2c0c607 100644
--- a/conda_env/exceptions.py
+++ b/conda_env/exceptions.py
@@ -6,17 +6,24 @@
 
 class CondaEnvException(CondaError):
     def __init__(self, message, *args, **kwargs):
-        msg = "Conda Env Exception: %s" % message
+        msg = "%s" % message
         super(CondaEnvException, self).__init__(msg, *args, **kwargs)
 
 
 class EnvironmentFileNotFound(CondaEnvException):
     def __init__(self, filename, *args, **kwargs):
-        msg = '{} file not found'.format(filename)
+        msg = "'{}' file not found".format(filename)
         self.filename = filename
         super(EnvironmentFileNotFound, self).__init__(msg, *args, **kwargs)
 
 
+class EnvironmentFileExtensionNotValid(CondaEnvException):
+    def __init__(self, filename, *args, **kwargs):
+        msg = "'{}' file extension must be one of '.txt', '.yaml' or '.yml'".format(filename)
+        self.filename = filename
+        super(EnvironmentFileExtensionNotValid, self).__init__(msg, *args, **kwargs)
+
+
 class NoBinstar(CondaError):
     def __init__(self):
         msg = 'The anaconda-client cli must be installed to perform this action'
diff --git a/conda_env/specs/__init__.py b/conda_env/specs/__init__.py
index dbf55c19bf0..4407e050e1d 100644
--- a/conda_env/specs/__init__.py
+++ b/conda_env/specs/__init__.py
@@ -8,28 +8,31 @@
 from .notebook import NotebookSpec
 from .requirements import RequirementsSpec
 from .yaml_file import YamlFileSpec
-from ..exceptions import EnvironmentFileNotFound, SpecNotFound
-
-
-all_specs = [
-    BinstarSpec,
-    NotebookSpec,
-    YamlFileSpec,
-    RequirementsSpec
-]
+from ..exceptions import (EnvironmentFileExtensionNotValid, EnvironmentFileNotFound,
+                          SpecNotFound)
 
 
 def detect(**kwargs):
-    # Check file existence if --file was provided
+    # Check file existence
     filename = kwargs.get('filename')
     if filename and not os.path.isfile(filename):
         raise EnvironmentFileNotFound(filename=filename)
 
+    # Check extensions
+    all_valid_exts = YamlFileSpec.extensions.union(RequirementsSpec.extensions)
+    fname, ext = os.path.splitext(filename)
+    if ext == '' or ext not in all_valid_exts:
+        raise EnvironmentFileExtensionNotValid(filename)
+    elif ext in YamlFileSpec.extensions:
+        specs = [YamlFileSpec]
+    elif ext in RequirementsSpec.extensions:
+        specs = [RequirementsSpec]
+    else:
+        specs = [NotebookSpec, BinstarSpec]
+
     # Check specifications
-    specs = []
-    for SpecClass in all_specs:
+    for SpecClass in specs:
         spec = SpecClass(**kwargs)
-        specs.append(spec)
         if spec.can_handle():
             return spec
 
diff --git a/conda_env/specs/requirements.py b/conda_env/specs/requirements.py
index 864325b8579..cf56aacd0fa 100644
--- a/conda_env/specs/requirements.py
+++ b/conda_env/specs/requirements.py
@@ -12,6 +12,7 @@ class RequirementsSpec(object):
     and returns an Environment object from it.
     '''
     msg = None
+    extensions = set(['.txt', ])
 
     def __init__(self, filename=None, name=None, **kwargs):
         self.filename = filename
diff --git a/conda_env/specs/yaml_file.py b/conda_env/specs/yaml_file.py
index aaabf976173..dd3ff855576 100644
--- a/conda_env/specs/yaml_file.py
+++ b/conda_env/specs/yaml_file.py
@@ -7,6 +7,7 @@
 
 class YamlFileSpec(object):
     _environment = None
+    extensions = set(('.yaml', '.yml'))
 
     def __init__(self, filename=None, **kwargs):
         self.filename = filename
diff --git a/tests/conda_env/support/invalid_keys.yml b/tests/conda_env/support/invalid_keys.yml
new file mode 100644
index 00000000000..8ac9ec04a04
--- /dev/null
+++ b/tests/conda_env/support/invalid_keys.yml
@@ -0,0 +1,6 @@
+names: nlp
+chanels:
+  - anaconda
+dependecies:
+  - nltk
+prefis: /something/miniconda/envs/test
diff --git a/tests/conda_env/support/valid_keys.yml b/tests/conda_env/support/valid_keys.yml
new file mode 100644
index 00000000000..664a1f82d66
--- /dev/null
+++ b/tests/conda_env/support/valid_keys.yml
@@ -0,0 +1,6 @@
+name: nlp
+channels:
+  - anaconda
+dependencies:
+  - nltk
+prefix: /something/miniconda/envs/test
diff --git a/tests/conda_env/test_cli.py b/tests/conda_env/test_cli.py
index f7928bde663..b12d7be069e 100644
--- a/tests/conda_env/test_cli.py
+++ b/tests/conda_env/test_cli.py
@@ -16,9 +16,11 @@
 from conda.exceptions import EnvironmentLocationNotFound
 from conda.install import rm_rf
 from conda_env.cli.main import create_parser, do_call as do_call_conda_env
-from conda_env.exceptions import EnvironmentFileNotFound
+from conda_env.exceptions import EnvironmentFileExtensionNotValid, EnvironmentFileNotFound
 from conda_env.yaml import load as yaml_load
 
+from . import support_file
+
 environment_1 = '''
 name: env-1
 dependencies:
@@ -36,6 +38,16 @@
   - malev
 '''
 
+environment_3_invalid = '''
+name: env-1
+dependecies:
+  - python
+  - flask
+channels:
+  - malev
+foo: bar
+'''
+
 test_env_name_1 = "env-1"
 test_env_name_2 = "snowflakes"
 test_env_name_3 = "env_foo"
@@ -264,7 +276,7 @@ def test_env_export(self):
 
         snowflake, e,  = run_env_command(Commands.ENV_EXPORT, test_env_name_2)
 
-        with tempfile.NamedTemporaryFile(mode="w", suffix="yml", delete=False) as env_yaml:
+        with tempfile.NamedTemporaryFile(mode="w", suffix=".yml", delete=False) as env_yaml:
             env_yaml.write(snowflake)
             env_yaml.flush()
             env_yaml.close()
@@ -292,7 +304,7 @@ def test_list(self):
 
         snowflake, e = run_conda_command(Commands.LIST, test_env_name_2, "-e")
 
-        with tempfile.NamedTemporaryFile(mode="w", suffix="txt", delete=False) as env_txt:
+        with tempfile.NamedTemporaryFile(mode="w", suffix=".txt", delete=False) as env_txt:
             env_txt.write(snowflake)
             env_txt.flush()
             env_txt.close()
@@ -320,7 +332,7 @@ def test_export_muti_channel(self):
 
         check1, e = run_conda_command(Commands.LIST, test_env_name_2, "--explicit")
 
-        with tempfile.NamedTemporaryFile(mode="w", suffix="yml", delete=False) as env_yaml:
+        with tempfile.NamedTemporaryFile(mode="w", suffix=".yml", delete=False) as env_yaml:
             env_yaml.write(snowflake)
             env_yaml.flush()
             env_yaml.close()
@@ -333,6 +345,16 @@ def test_export_muti_channel(self):
         check2, e = run_conda_command(Commands.LIST, test_env_name_2, "--explicit")
         self.assertEqual(check1, check2)
 
+    def test_non_existent_file(self):
+        with self.assertRaises(EnvironmentFileNotFound):
+            run_env_command(Commands.ENV_CREATE, 'i_do_not_exist.yml')
+
+    def test_invalid_extensions(self):
+        with tempfile.NamedTemporaryFile(mode="w", suffix=".ymla", delete=False) as env_yaml:
+            with self.assertRaises(EnvironmentFileExtensionNotValid):
+                run_env_command(Commands.ENV_CREATE, env_yaml.name)
+
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/conda_env/test_env.py b/tests/conda_env/test_env.py
index af5cd728215..b0619af18a1 100644
--- a/tests/conda_env/test_env.py
+++ b/tests/conda_env/test_env.py
@@ -25,8 +25,20 @@ def write(self, chunk):
         self.output += chunk.decode('utf-8')
 
 
+def get_environment(filename):
+    return env.from_file(support_file(filename))
+
+
 def get_simple_environment():
-    return env.from_file(support_file('simple.yml'))
+    return get_environment('simple.yml')
+
+
+def get_valid_keys_environment():
+    return get_environment('valid_keys.yml')
+
+
+def get_invalid_keys_environment():
+    return get_environment('invalid_keys.yml')
 
 
 class from_file_TestCase(unittest.TestCase):
@@ -215,6 +227,18 @@ def test_dependencies_update_after_adding(self):
         e.dependencies.add('bar')
         assert 'bar' in e.dependencies['conda']
 
+    def test_valid_keys(self):
+        e = get_valid_keys_environment()
+        e_dict = e.to_dict()
+        for key in env.VALID_KEYS:
+            assert key in e_dict
+
+    def test_invalid_keys(self):
+        e = get_invalid_keys_environment()
+        e_dict = e.to_dict()
+        assert 'name' in e_dict
+        assert len(e_dict) == 1
+
 
 class DirectoryTestCase(unittest.TestCase):
     directory = support_file('example')