diff --git a/src/Meziantou.Analyzer/Internals/CultureSensitiveFormattingContext.cs b/src/Meziantou.Analyzer/Internals/CultureSensitiveFormattingContext.cs
index 8a8d6f1a3..748f11e02 100755
--- a/src/Meziantou.Analyzer/Internals/CultureSensitiveFormattingContext.cs
+++ b/src/Meziantou.Analyzer/Internals/CultureSensitiveFormattingContext.cs
@@ -113,6 +113,30 @@ public bool IsCultureSensitiveOperation(IOperation operation, CultureSensitiveOp
                 if (invocation.Arguments.Length == 1 && invocation.Arguments[0].Value.Type.IsEqualTo(StringBuilder_AppendInterpolatedStringHandlerSymbol) && !IsCultureSensitiveOperation(invocation.Arguments[0].Value, options))
                     return false;
             }
+            else if (methodName is "AppendFormat" && invocation.TargetMethod.ContainingType.IsEqualTo(StringBuilderSymbol) && invocation.Arguments.Length > 0)
+            {
+                if (invocation.Arguments.Length == 1)
+                    return false;
+
+                if (invocation.TargetMethod.Parameters.Length == 2 && invocation.Arguments[1].Parameter?.Type is IArrayTypeSymbol && invocation.Arguments[1].Value is IArrayCreationOperation appendFormatArrayCreation)
+                {
+                    var initializer = appendFormatArrayCreation.Initializer;
+                    if (initializer is null)
+                        return true;
+
+                    return initializer.ElementValues.Any(arg => IsCultureSensitiveOperation(arg.UnwrapImplicitConversionOperations(), options));
+                }
+#if ROSLYN_4_14_OR_GREATER
+                else if (invocation.TargetMethod.Parameters.Length == 2 && invocation.Arguments[1].Value is ICollectionExpressionOperation appendFormatCollectionExpression)
+                {
+                    return appendFormatCollectionExpression.Elements.Any(arg => IsCultureSensitiveOperation(arg.UnwrapImplicitConversionOperations(), options));
+                }
+#endif
+                else
+                {
+                    return invocation.Arguments.Skip(1).Any(arg => IsCultureSensitiveOperation(arg.Value.UnwrapImplicitConversionOperations(), options));
+                }
+            }
             else if (methodName is "Format" && invocation.TargetMethod.IsStatic && invocation.TargetMethod.ContainingType.IsString() && invocation.Arguments.Length > 0)
             {
                 if (invocation.TargetMethod.Parameters[0].Type.IsEqualTo(FormatProviderSymbol))
diff --git a/tests/Meziantou.Analyzer.Test/Rules/UseIFormatProviderAnalyzerTests.cs b/tests/Meziantou.Analyzer.Test/Rules/UseIFormatProviderAnalyzerTests.cs
index 71b199693..37544206b 100755
--- a/tests/Meziantou.Analyzer.Test/Rules/UseIFormatProviderAnalyzerTests.cs
+++ b/tests/Meziantou.Analyzer.Test/Rules/UseIFormatProviderAnalyzerTests.cs
@@ -58,7 +58,9 @@ await CreateProjectBuilder()
     [InlineData(""" [|System.DateTime.TryParse("", out _)|] """)]
     [InlineData(""" [|System.DateTimeOffset.TryParse("", out _)|] """)]
     [InlineData(""" [|"".ToLower()|] """)]
-    [InlineData(""" [|new System.Text.StringBuilder().AppendFormat("{0}", 10)|] """)]
+    [InlineData(""" [|new System.Text.StringBuilder().AppendFormat("{0}", -1)|] """)]
+    [InlineData(""" new System.Text.StringBuilder().AppendFormat("{0}", 10) """)]
+    [InlineData(""" new System.Text.StringBuilder().AppendFormat("{0} / {1}", "X", "Y") """)]
     [InlineData(""" System.DayOfWeek.Monday.ToString() """)]
     [InlineData(""" default(System.DateTime).ToString("o") """)]
     [InlineData(""" default(System.DateTime).ToString("O") """)]