diff --git a/README.md b/README.md
index 6db5f5e..8c89dc3 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,11 @@ The action takes the following inputs:
     supported on all operating systems; see https://dart.dev/tools/sdk/archive
     for valid combinations.
 
+  * `signed`: Whether to install signed SDK binaries (defaults to true).
+    Unsigned binaries may not work on all operating systems. This option is
+    exposed for core packages that need to test against unreleased dev SDKs that
+    are automatically rolled in to the flutter CI systems.
+
 ## Basic example
 
 Install the latest stable SDK, and run Hello World.
@@ -169,6 +174,9 @@ jobs:
 
 # Version history
 
+## v1.1
+  * Added support for installing unsigned dev SDKs.
+
 ## v1.0
   * Promoted to 1.0 stable.
 
diff --git a/action.yml b/action.yml
index 49a3c7f..bdaecc4 100644
--- a/action.yml
+++ b/action.yml
@@ -12,8 +12,12 @@ inputs:
     description: "The CPU architecture ('x64', 'ia32', 'arm', or 'arm64')."
     required: false
     default: "x64"
+  signed:
+    description: "Whether to install a signed or unsigned Dart SDK build. Used to install unpublished dev releases."
+    required: false
+    default: true
 runs:
   using: "composite"
   steps:
-    - run: $GITHUB_ACTION_PATH/setup.sh ${{ inputs.sdk }} ${{ runner.os }} ${{ inputs.architecture }}
+    - run: $GITHUB_ACTION_PATH/setup.sh ${{ inputs.sdk }} ${{ runner.os }} ${{ inputs.architecture }} ${{inputs.signed }}
       shell: bash
diff --git a/setup.sh b/setup.sh
index 6a0334e..fefbe11 100755
--- a/setup.sh
+++ b/setup.sh
@@ -9,14 +9,15 @@
 # Bash script that downloads and does setup for a Dart SDK.                   #
 # Takes three params; first listed is the default:                            #
 # $1: Dart SDK version/channel: stable|beta|dev|main|<version_string>         #
-# $2: Dart channel (DEPRECATED): stable|beta|dev                              #
-# $3: OS: Linux|Windows|macOS                                                 #
-# $4: ARCH: x64|ia32                                                          #
+# $2: OS: Linux|Windows|macOS                                                 #
+# $3: ARCH: x64|ia32                                                          #
+# $4: SIGNED: true|false  (optional, defaults to true)                        #
 ###############################################################################
 
 # Parse SDK and version args.
 SDK="${1:-stable}"
 VERSION=
+SIGNED="${4:-true}"
 if [[ $SDK == stable || $SDK == beta || $SDK == dev || $SDK == main ]]
 then
   CHANNEL=$SDK
@@ -47,12 +48,14 @@ echo "Installing Dart SDK version \"${VERSION}\" from the ${CHANNEL} channel on
 # https://dart.dev/tools/sdk/archive#download-urls
 PREFIX="https://storage.googleapis.com/dart-archive/channels"
 BUILD="sdk/dartsdk-${OS}-${ARCH}-release.zip"
-if [[ $SDK == main ]]
+CHANNEL_FOLDER="${CHANNEL/main/be}"
+if [[ $SIGNED == false || $SDK == main ]]
 then
-  URL="${PREFIX}/be/raw/latest/${BUILD}"
+  BINARIES_FOLDER=raw
 else
-  URL="${PREFIX}/${CHANNEL}/release/${VERSION}/${BUILD}"
+  BINARIES_FOLDER=release
 fi
+URL="${PREFIX}/${CHANNEL_FOLDER}/${BINARIES_FOLDER}/${VERSION}/${BUILD}"
 echo "Downloading ${URL}..."
 
 # Download installation zip.