diff --git a/src/AutoMapper/Licensing/LicenseAccessor.cs b/src/AutoMapper/Licensing/LicenseAccessor.cs
index ba4bfa152c..8ee939b1e1 100644
--- a/src/AutoMapper/Licensing/LicenseAccessor.cs
+++ b/src/AutoMapper/Licensing/LicenseAccessor.cs
@@ -52,11 +52,22 @@ private License Initialize()
     /// Resolves the license key from, in order of precedence: the explicitly configured value,
     /// the product-specific <c>AUTOMAPPER_LICENSE_KEY</c> environment variable, then the shared
     /// <c>LUCKYPENNY_LICENSE_KEY</c> environment variable (usable across Lucky Penny products).
+    /// Whitespace is removed from each value, and empty values are treated as unset.
     /// </summary>
     internal static string ResolveLicenseKey(string explicitKey) =>
-        explicitKey
-        ?? Environment.GetEnvironmentVariable(AutoMapperLicenseKeyEnvVariable)
-        ?? Environment.GetEnvironmentVariable(SharedLicenseKeyEnvVariable);
+        NormalizeLicenseKey(explicitKey)
+        ?? NormalizeLicenseKey(Environment.GetEnvironmentVariable(AutoMapperLicenseKeyEnvVariable))
+        ?? NormalizeLicenseKey(Environment.GetEnvironmentVariable(SharedLicenseKeyEnvVariable));
+
+    private static string NormalizeLicenseKey(string key)
+    {
+        if (string.IsNullOrWhiteSpace(key))
+        {
+            return null;
+        }
+
+        return new string(key.Where(c => !char.IsWhiteSpace(c)).ToArray());
+    }
 
     private Claim[] ValidateKey(string licenseKey)
     {
@@ -105,4 +116,4 @@ private Claim[] ValidateKey(string licenseKey)
         }
     }
 
-}
\ No newline at end of file
+}
diff --git a/src/UnitTests/Licensing/LicenseKeyEnvironmentVariableTests.cs b/src/UnitTests/Licensing/LicenseKeyEnvironmentVariableTests.cs
index 4d1bbad3f3..5d93ef86ac 100644
--- a/src/UnitTests/Licensing/LicenseKeyEnvironmentVariableTests.cs
+++ b/src/UnitTests/Licensing/LicenseKeyEnvironmentVariableTests.cs
@@ -10,6 +10,76 @@ public class LicenseKeyEnvironmentVariableTests
 {
     private const string AutoMapperEnvVar = LicenseAccessor.AutoMapperLicenseKeyEnvVariable;
     private const string SharedEnvVar = LicenseAccessor.SharedLicenseKeyEnvVariable;
+    private const string CleanKey = "header.pay-load.sign_ature";
+
+    public static TheoryData<string> KeysWithWhitespace => new()
+    {
+        CleanKey + "\n",
+        CleanKey + "\r\n",
+        CleanKey + " ",
+        CleanKey + "\t",
+        " \t" + CleanKey,
+        "header.\r\npay-\nload.sign_\tature",
+        "\u00a0header.\u2003pay-load.sign_ature\u2028"
+    };
+
+    [Theory]
+    [MemberData(nameof(KeysWithWhitespace))]
+    public void ExplicitKey_StripsWhitespace_AndTakesPrecedence(string key)
+    {
+        WithEnvironment(autoMapper: "env-automapper-key", shared: "env-shared-key", () =>
+            LicenseAccessor.ResolveLicenseKey(key).ShouldBe(CleanKey));
+    }
+
+    [Theory]
+    [MemberData(nameof(KeysWithWhitespace))]
+    public void AutoMapperEnvironmentVariable_StripsWhitespace_AndTakesPrecedence(string key)
+    {
+        WithEnvironment(autoMapper: key, shared: "env-shared-key", () =>
+            LicenseAccessor.ResolveLicenseKey(null).ShouldBe(CleanKey));
+    }
+
+    [Theory]
+    [MemberData(nameof(KeysWithWhitespace))]
+    public void SharedEnvironmentVariable_StripsWhitespace(string key)
+    {
+        WithEnvironment(autoMapper: null, shared: key, () =>
+            LicenseAccessor.ResolveLicenseKey(null).ShouldBe(CleanKey));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData(" ")]
+    [InlineData("\t\r\n")]
+    [InlineData("\u00a0\u2003\u2028")]
+    public void BlankExplicitKey_FallsBackToAutoMapperEnvironmentVariable(string key)
+    {
+        WithEnvironment(autoMapper: " env-automapper-key\n", shared: "env-shared-key", () =>
+            LicenseAccessor.ResolveLicenseKey(key).ShouldBe("env-automapper-key"));
+    }
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData(" ")]
+    [InlineData("\t\r\n")]
+    [InlineData("\u00a0\u2003\u2028")]
+    public void BlankHigherPrecedenceKeys_FallBackToSharedEnvironmentVariable(string key)
+    {
+        WithEnvironment(autoMapper: key, shared: " env-shared-key\n", () =>
+            LicenseAccessor.ResolveLicenseKey(key).ShouldBe("env-shared-key"));
+    }
+
+    [Theory]
+    [InlineData("")]
+    [InlineData(" ")]
+    [InlineData("\t\r\n")]
+    [InlineData("\u00a0\u2003\u2028")]
+    public void ReturnsNull_WhenAllKeysAreBlank(string key)
+    {
+        WithEnvironment(autoMapper: key, shared: key, () =>
+            LicenseAccessor.ResolveLicenseKey(key).ShouldBeNull());
+    }
 
     [Fact]
     public void ExplicitKey_TakesPrecedence_OverBothEnvironmentVariables()