diff --git a/src/Microsoft.Identity.Web/Constants/Constants.cs b/src/Microsoft.Identity.Web/Constants/Constants.cs
index e417617ad..377475bb6 100644
--- a/src/Microsoft.Identity.Web/Constants/Constants.cs
+++ b/src/Microsoft.Identity.Web/Constants/Constants.cs
@@ -58,8 +58,13 @@ internal static class Constants
         public const string Bearer = "Bearer";
         public const string LoginHint = "loginHint";
         public const string DomainHint = "domainHint";
+        public const string Authorization = "Authorization";
 
-        // Blazor challenge uri
+        // Blazor challenge URI
         public const string BlazorChallengeUri = "MicrosoftIdentity/Account/Challenge?redirectUri=";
+
+        // Microsoft Graph
+        public const string UserReadScope = "user.read";
+        public const string GraphBaseUrlV1 = "https://graph.microsoft.com/v1.0";
     }
 }
diff --git a/src/Microsoft.Identity.Web/Constants/IDWebErrorMessage.cs b/src/Microsoft.Identity.Web/Constants/IDWebErrorMessage.cs
index 41355123c..5c6eb766f 100644
--- a/src/Microsoft.Identity.Web/Constants/IDWebErrorMessage.cs
+++ b/src/Microsoft.Identity.Web/Constants/IDWebErrorMessage.cs
@@ -31,6 +31,7 @@ internal static class IDWebErrorMessage
         public const string UnauthenticatedUser = "IDW10204:The user is unauthenticated. The HttpContext does not contain any claims. ";
         public const string BlazorServerBaseUriNotSet = "IDW10205: Using Blazor server but the base URI was not properly set. ";
         public const string BlazorServerUserNotSet = "IDW10206: Using Blazor server but the user was not properly set. ";
+        public const string CalledApiScopesAreNull = "IDW10207: The CalledApiScopes cannot be null. ";
 
         // Token Validation IDW10300 = "IDW10300:"
         public const string IssuerMetadataUrlIsRequired = "IDW10301: Azure AD Issuer metadata address URL is required. ";
diff --git a/src/Microsoft.Identity.Web/MicrosoftGraph/MicrosoftGraphServiceExtensions.cs b/src/Microsoft.Identity.Web/MicrosoftGraph/MicrosoftGraphServiceExtensions.cs
index af08ebb5c..404c98da4 100644
--- a/src/Microsoft.Identity.Web/MicrosoftGraph/MicrosoftGraphServiceExtensions.cs
+++ b/src/Microsoft.Identity.Web/MicrosoftGraph/MicrosoftGraphServiceExtensions.cs
@@ -10,16 +10,16 @@
 namespace Microsoft.Identity.Web
 {
     /// <summary>
-    /// Extensions methods on a MicrososoftAppCallingWebApiAuthenticationBuilder builder
+    /// Extensions methods on a MicrosoftIdentityAppCallingWebApiAuthenticationBuilder builder
     /// to add support to call Microsoft Graph.
     /// </summary>
     public static class MicrosoftGraphServiceExtensions
     {
         /// <summary>
-        /// Add support to calls Microsoft graph. From a named option and a configuration section.
+        /// Add support to call Microsoft Graph. From a named option and a configuration section.
         /// </summary>
         /// <param name="builder">Builder.</param>
-        /// <param name="configurationSection">Configuraiton section.</param>
+        /// <param name="configurationSection">Configuration section.</param>
         /// <returns>The builder to chain.</returns>
         public static MicrosoftIdentityAppCallsWebApiAuthenticationBuilder AddMicrosoftGraphServiceClient(
             this MicrosoftIdentityAppCallsWebApiAuthenticationBuilder builder,
@@ -30,16 +30,16 @@ public static MicrosoftIdentityAppCallsWebApiAuthenticationBuilder AddMicrosoftG
         }
 
         /// <summary>
-        /// Add support to calls Microsoft graph. From a base graph Url and a default scope.
+        /// Add support to call Microsoft Graph. From a base Graph URL and a default scope.
         /// </summary>
         /// <param name="builder">Builder.</param>
         /// <param name="graphBaseUrl">Named instance of option.</param>
-        /// <param name="defaultScopes">Configuraiton section.</param>
+        /// <param name="defaultScopes">Configuration section.</param>
         /// <returns>The builder to chain.</returns>
         public static MicrosoftIdentityAppCallsWebApiAuthenticationBuilder AddMicrosoftGraphServiceClient(
             this MicrosoftIdentityAppCallsWebApiAuthenticationBuilder builder,
-            string graphBaseUrl = "https://graph.microsoft.com/v1.0",
-            string defaultScopes = "user.read")
+            string graphBaseUrl = Constants.GraphBaseUrlV1,
+            string defaultScopes = Constants.UserReadScope)
         {
             return builder.AddMicrosoftGraphServiceClient(
                 options =>
@@ -50,7 +50,7 @@ public static MicrosoftIdentityAppCallsWebApiAuthenticationBuilder AddMicrosoftG
         }
 
         /// <summary>
-        /// Add support to calls Microsoft graph. From a named options and a configuraiton method.
+        /// Add support to call Microsoft Graph. From a named options and a configuration method.
         /// </summary>
         /// <param name="builder">Builder.</param>
         /// <param name="configureMicrosoftGraphOptions">Method to configure the options.</param>
@@ -76,7 +76,7 @@ public static MicrosoftIdentityAppCallsWebApiAuthenticationBuilder AddMicrosoftG
                 var microsoftGraphOptions = options.Value;
                 if (microsoftGraphOptions.Scopes == null)
                 {
-                    throw new ArgumentException("CalledApiScopes should not be null.");
+                    throw new ArgumentException(IDWebErrorMessage.CalledApiScopesAreNull);
                 }
 
                 string graphBaseUrl = microsoftGraphOptions.BaseUrl;
diff --git a/src/Microsoft.Identity.Web/MicrosoftGraph/TokenAcquisitionCredentialProvider.cs b/src/Microsoft.Identity.Web/MicrosoftGraph/TokenAcquisitionCredentialProvider.cs
index 73a8681d0..59e5594bd 100644
--- a/src/Microsoft.Identity.Web/MicrosoftGraph/TokenAcquisitionCredentialProvider.cs
+++ b/src/Microsoft.Identity.Web/MicrosoftGraph/TokenAcquisitionCredentialProvider.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT License.
 
 using System.Collections.Generic;
+using System.Globalization;
 using System.Net.Http;
 using System.Threading.Tasks;
 using Microsoft.Graph;
@@ -30,8 +31,12 @@ public TokenAcquisitionCredentialProvider(ITokenAcquisition tokenAcquisition, IE
         public async Task AuthenticateRequestAsync(HttpRequestMessage request)
         {
             request.Headers.Add(
-                "Authorization",
-                $"Bearer {await _tokenAcquisition.GetAccessTokenForUserAsync(_initialScopes).ConfigureAwait(false)}");
+                Constants.Authorization,
+                string.Format(
+                    CultureInfo.InvariantCulture,
+                    "{0}{1}",
+                    Constants.Bearer,
+                    await _tokenAcquisition.GetAccessTokenForUserAsync(_initialScopes).ConfigureAwait(false)));
         }
     }
 }