diff --git a/conda_smithy/configure_feedstock.py b/conda_smithy/configure_feedstock.py
index ff0c1e0c2..44a9f1285 100755
--- a/conda_smithy/configure_feedstock.py
+++ b/conda_smithy/configure_feedstock.py
@@ -11,6 +11,25 @@
 
 import conda.api
 import conda.config
+
+try:
+    from conda.base.constants import (
+        DEFAULT_CHANNELS_UNIX,
+        DEFAULT_CHANNELS_WIN,
+    )
+except ImportError:
+    # old conda
+    DEFAULT_CHANNELS_UNIX = (
+        'https://repo.continuum.io/pkgs/free',
+        'https://repo.continuum.io/pkgs/pro',
+    )
+
+    DEFAULT_CHANNELS_WIN = (
+        'https://repo.continuum.io/pkgs/free',
+        'https://repo.continuum.io/pkgs/pro',
+        'https://repo.continuum.io/pkgs/msys2',
+    )
+
 import conda_build.metadata
 try:
     import conda_build.api
@@ -44,7 +63,11 @@ def render_run_docker_build(jinja_env, forge_config, forge_dir):
     meta = forge_config['package']
     with fudge_subdir('linux-64', build_config=meta_config(meta)):
         meta.parse_again()
-        matrix = compute_build_matrix(meta, forge_config.get('matrix'))
+        matrix = compute_build_matrix(
+            meta,
+            forge_config.get('matrix'),
+            forge_config.get('channels', {}).get('sources', tuple())
+        )
         cases_not_skipped = []
         for case in matrix:
             pkgs, vars = split_case(case)
@@ -145,7 +168,11 @@ def render_circle(jinja_env, forge_config, forge_dir):
     meta = forge_config['package']
     with fudge_subdir('linux-64', build_config=meta_config(meta)):
         meta.parse_again()
-        matrix = compute_build_matrix(meta, forge_config.get('matrix'))
+        matrix = compute_build_matrix(
+            meta,
+            forge_config.get('matrix'),
+            forge_config.get('channels', {}).get('sources', tuple())
+        )
 
         cases_not_skipped = []
         for case in matrix:
@@ -198,7 +225,11 @@ def render_travis(jinja_env, forge_config, forge_dir):
     meta = forge_config['package']
     with fudge_subdir('osx-64', build_config=meta_config(meta)):
         meta.parse_again()
-        matrix = compute_build_matrix(meta, forge_config.get('matrix'))
+        matrix = compute_build_matrix(
+            meta,
+            forge_config.get('matrix'),
+            forge_config.get('channels', {}).get('sources', tuple())
+        )
 
         cases_not_skipped = []
         for case in matrix:
@@ -330,7 +361,11 @@ def render_appveyor(jinja_env, forge_config, forge_dir):
     for platform, arch in [['win-32', 'x86'], ['win-64', 'x64']]:
         with fudge_subdir(platform, build_config=meta_config(meta)):
             meta.parse_again()
-            matrix = compute_build_matrix(meta, forge_config.get('matrix'))
+            matrix = compute_build_matrix(
+                meta,
+                forge_config.get('matrix'),
+                forge_config.get('channels', {}).get('sources', tuple())
+            )
 
             cases_not_skipped = []
             for case in matrix:
@@ -500,8 +535,26 @@ def meta_of_feedstock(forge_dir, config=None):
     return meta
 
 
-def compute_build_matrix(meta, existing_matrix=None):
-    index = conda.api.get_index()
+def compute_build_matrix(meta, existing_matrix=None, channel_sources=tuple()):
+    channel_sources = tuple(channel_sources)
+
+    # Override what `defaults` means depending on the platform used.
+    try:
+        i = channel_sources.index("defaults")
+
+        defaults = DEFAULT_CHANNELS_UNIX
+        if meta_config(meta).subdir.startswith("win"):
+            defaults = DEFAULT_CHANNELS_WIN
+
+        channel_sources = (
+            channel_sources[:i] +
+            defaults +
+            channel_sources[i+1:]
+        )
+    except ValueError:
+        pass
+
+    index = conda.api.get_index(channel_urls=channel_sources)
     mtx = special_case_version_matrix(meta, index)
     mtx = list(filter_cases(mtx, ['python >=2.7,<3|>=3.4', 'numpy >=1.10']))
     if existing_matrix:
@@ -529,7 +582,8 @@ def main(forge_file_directory):
               'travis': {},
               'circle': {},
               'appveyor': {},
-              'channels': {'sources': ['conda-forge'], 'targets': [['conda-forge', 'main']]},
+              'channels': {'sources': ['conda-forge', 'defaults'],
+                           'targets': [['conda-forge', 'main']]},
               'github': {'user_or_org': 'conda-forge', 'repo_name': ''},
               'recipe_dir': recipe_dir}
     forge_dir = os.path.abspath(forge_file_directory)
diff --git a/conda_smithy/templates/appveyor.yml.tmpl b/conda_smithy/templates/appveyor.yml.tmpl
index 12c69ebda..45406f51b 100644
--- a/conda_smithy/templates/appveyor.yml.tmpl
+++ b/conda_smithy/templates/appveyor.yml.tmpl
@@ -41,17 +41,10 @@ install:
     # Cywing's git breaks conda-build. (See https://github.com/conda-forge/conda-smithy-feedstock/pull/2.)
     - cmd: rmdir C:\cygwin /s /q
 
-    # Add our channels.
+    # Add a hack to update conda as the included copy is too old.
     - cmd: set "OLDPATH=%PATH%"
     - cmd: set "PATH=%CONDA_INSTALL_LOCN%\\Scripts;%CONDA_INSTALL_LOCN%\\Library\\bin;%PATH%"
-    - cmd: conda config --set show_channel_urls true
-    {%- for channel in channels.get('sources', [])|reverse %}
-    - cmd: conda config --add channels {{ channel }}{% endfor %}
-
-    # Add a hack to switch to `conda` version `4.1.12` before activating.
-    # This is required to handle a long path activation issue.
-    # Please see PR ( https://github.com/conda/conda/pull/3349 ).
-    - cmd: conda install --yes --quiet conda=4.1.12
+    - cmd: conda update --yes --quiet conda
     - cmd: set "PATH=%OLDPATH%"
     - cmd: set "OLDPATH="
 
@@ -59,6 +52,13 @@ install:
     - cmd: call %CONDA_INSTALL_LOCN%\Scripts\activate.bat
     - cmd: set PYTHONUNBUFFERED=1
 
+    # Add our channels.
+    - cmd: conda config --set show_channel_urls true
+    - cmd: conda config --remove channels defaults
+    {%- for channel in channels.get('sources', [])|reverse %}
+    - cmd: conda config --add channels {{ channel }}{% endfor %}
+
+    # Configure the VM.
     - cmd: conda install -n root --quiet --yes obvious-ci
     - cmd: conda install -n root --quiet --yes conda-forge-build-setup
     {% if build_setup -%}
diff --git a/conda_smithy/templates/run_docker_build.tmpl b/conda_smithy/templates/run_docker_build.tmpl
index 451b45282..6b7a009b1 100644
--- a/conda_smithy/templates/run_docker_build.tmpl
+++ b/conda_smithy/templates/run_docker_build.tmpl
@@ -16,7 +16,6 @@ channels:
 {%- for channel in channels.get('sources', []) %}
  - {{ channel }}
 {%- endfor %}
- - defaults # As we need conda-build
 
 conda-build:
  root-dir: /feedstock_root/build_artefacts
diff --git a/conda_smithy/templates/travis.yml.tmpl b/conda_smithy/templates/travis.yml.tmpl
index 36e8a6a3d..b1f30dab8 100644
--- a/conda_smithy/templates/travis.yml.tmpl
+++ b/conda_smithy/templates/travis.yml.tmpl
@@ -44,7 +44,7 @@ install:
       bash $MINICONDA_FILE -b
 
       source /Users/travis/miniconda3/bin/activate root
-
+      conda config --remove channels defaults
       {%- for channel in channels.get('sources', [])|reverse %}
       conda config --add channels {{ channel }}
       {%- endfor %}