diff --git a/CliFx.Analyzers/CommandSchemaAnalyzer.cs b/CliFx.Analyzers/CommandSchemaAnalyzer.cs
index 52b62eb..f299279 100644
--- a/CliFx.Analyzers/CommandSchemaAnalyzer.cs
+++ b/CliFx.Analyzers/CommandSchemaAnalyzer.cs
@@ -206,7 +206,7 @@ namespace CliFx.Analyzers
             // Duplicate environment variable name
             var duplicateEnvironmentVariableNameOptions = options
                 .Where(p => !string.IsNullOrWhiteSpace(p.EnvironmentVariableName))
-                .GroupBy(p => p.EnvironmentVariableName, StringComparer.OrdinalIgnoreCase)
+                .GroupBy(p => p.EnvironmentVariableName, StringComparer.Ordinal)
                 .Where(g => g.Count() > 1)
                 .SelectMany(g => g.AsEnumerable())
                 .ToArray();
diff --git a/CliFx.Tests/EnvironmentVariablesSpecs.cs b/CliFx.Tests/EnvironmentVariablesSpecs.cs
index 67b4014..f8d1b52 100644
--- a/CliFx.Tests/EnvironmentVariablesSpecs.cs
+++ b/CliFx.Tests/EnvironmentVariablesSpecs.cs
@@ -89,5 +89,27 @@ namespace CliFx.Tests
                 Option = $"foo{Path.PathSeparator}bar"
             });
         }
+        
+        [Fact]
+        public void Option_can_use_a_specific_environment_variable_as_fallback_while_respecting_case()
+        {
+            // Arrange
+            const string expected = "foobar";
+            var input = CommandInput.Empty;
+            var envVars = new Dictionary<string, string>
+            {
+                ["ENV_OPT"] = expected,
+                ["env_opt"] = "2"
+            };
+
+            // Act
+            var instance = CommandHelper.ResolveCommand<EnvironmentVariableCommand>(input, envVars);
+
+            // Assert
+            instance.Should().BeEquivalentTo(new EnvironmentVariableCommand
+            {
+                Option = expected
+            });
+        }
     }
-}
\ No newline at end of file
+}
diff --git a/CliFx/CliApplication.cs b/CliFx/CliApplication.cs
index 228ab5b..593ed93 100644
--- a/CliFx/CliApplication.cs
+++ b/CliFx/CliApplication.cs
@@ -218,9 +218,10 @@ namespace CliFx
         /// </remarks>
         public async ValueTask<int> RunAsync(IReadOnlyList<string> commandLineArguments)
         {
+            // Environment variable names are case-insensitive on Windows but are case-sensitive on Linux and macOS
             var environmentVariables = Environment.GetEnvironmentVariables()
                 .Cast<DictionaryEntry>()
-                .ToDictionary(e => (string) e.Key, e => (string) e.Value, StringComparer.OrdinalIgnoreCase);
+                .ToDictionary(e => (string) e.Key, e => (string) e.Value, StringComparer.Ordinal);
 
             return await RunAsync(commandLineArguments, environmentVariables);
         }
@@ -264,4 +265,4 @@ namespace CliFx
             public ValueTask ExecuteAsync(IConsole console) => default;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/CliFx/Domain/CommandOptionSchema.cs b/CliFx/Domain/CommandOptionSchema.cs
index e4b95fa..bc79f57 100644
--- a/CliFx/Domain/CommandOptionSchema.cs
+++ b/CliFx/Domain/CommandOptionSchema.cs
@@ -45,7 +45,7 @@ namespace CliFx.Domain
 
         public bool MatchesEnvironmentVariableName(string environmentVariableName) =>
             !string.IsNullOrWhiteSpace(EnvironmentVariableName) &&
-            string.Equals(EnvironmentVariableName, environmentVariableName, StringComparison.OrdinalIgnoreCase);
+            string.Equals(EnvironmentVariableName, environmentVariableName, StringComparison.Ordinal);
 
         public string GetUserFacingDisplayString()
         {