diff --git a/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexParser.cs b/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexParser.cs
index 69511af80983bd..eaf5f23d3c639f 100644
--- a/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexParser.cs
+++ b/src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexParser.cs
@@ -1000,8 +1000,9 @@ private RegexNode ScanReplacement()
                         --_pos;
 
                         nodeType = RegexNodeKind.Group;
-                        // Disallow options in the children of a testgroup node
-                        if (_group!.Kind != RegexNodeKind.ExpressionConditional)
+                        // While parsing the test of a conditional (ExpressionConditional with no children yet),
+                        // disallow inline options; allow them once the test has been parsed and in the yes/no branches.
+                        if (_group!.Kind != RegexNodeKind.ExpressionConditional || _group.ChildCount() > 0)
                         {
                             ScanOptions();
                         }
diff --git a/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/Regex.Match.Tests.cs b/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/Regex.Match.Tests.cs
index c03f22a893ac1a..0a5e4e4d7e6fe5 100644
--- a/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/Regex.Match.Tests.cs
+++ b/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/Regex.Match.Tests.cs
@@ -898,6 +898,16 @@ public static IEnumerable<object[]> Match_MemberData()
                 yield return (@"(?(\w+)\w+)dog", "catdog", RegexOptions.None, 0, 6, true, "catdog");
                 yield return (@"(?(abc)\w+|\w{0,2})dog", "catdog", RegexOptions.None, 0, 6, true, "atdog");
                 yield return (@"(?(abc)cat|\w{0,2})dog", "catdog", RegexOptions.None, 0, 6, true, "atdog");
+
+                // Inline options inside conditional branches
+                yield return (@"(?(cat)(?i)CAT|dog)", "cat", RegexOptions.None, 0, 3, true, "cat");
+                yield return (@"(?(cat)(?i)cat|dog)", "dog", RegexOptions.None, 0, 3, true, "dog");
+                yield return (@"(?(cat)cat|(?i)dog)", "DOG", RegexOptions.None, 0, 3, true, "DOG");
+                yield return (@"(?(cat)(?i:CAT)|dog)", "cat", RegexOptions.None, 0, 3, true, "cat");
+                yield return (@"(?(?=cat)(?i)CAT|dog)", "cat", RegexOptions.None, 0, 3, true, "cat");
+                yield return (@"(cat)?(?(1)(?i)dog|pig)", "catDOG", RegexOptions.None, 0, 6, true, "catDOG");
+                yield return (@"(cat)?(?(1)(?i)dog|pig)", "pig", RegexOptions.None, 0, 3, true, "pig");
+                yield return (@"(?((?i)cat)CAT|dog)", "CAT", RegexOptions.None, 0, 3, true, "CAT");
                 yield return ("(a|ab|abc|abcd)d", "abcd", RegexOptions.RightToLeft, 0, 4, true, "abcd");
 
                 yield return ("(?>(?:a|ab|abc|abcd))d", "abcd", RegexOptions.None, 0, 4, false, string.Empty);
diff --git a/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/RegexParserTests.netcoreapp.cs b/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/RegexParserTests.netcoreapp.cs
index a3e02e8439e2a9..06e157a7587659 100644
--- a/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/RegexParserTests.netcoreapp.cs
+++ b/src/libraries/System.Text.RegularExpressions/tests/FunctionalTests/RegexParserTests.netcoreapp.cs
@@ -26,6 +26,7 @@ public partial class RegexParserTests
         [InlineData(@"(?(?X))", RegexOptions.None, RegexParseError.InvalidGroupingConstruct, 5)]
         [InlineData(@"(?(?n))", RegexOptions.None, RegexParseError.InvalidGroupingConstruct, 5)]
         [InlineData(@"(?(?m))", RegexOptions.None, RegexParseError.InvalidGroupingConstruct, 5)]
+        [InlineData(@"(?(?i)yes|no)", RegexOptions.None, RegexParseError.InvalidGroupingConstruct, 5)] // does not throw on .NET Framework, but that is a parser bug there
         [InlineData("(?<-", RegexOptions.None, RegexParseError.InvalidGroupingConstruct, 3)]
         [InlineData("(?<-", RegexOptions.IgnorePatternWhitespace, RegexParseError.InvalidGroupingConstruct, 3)]
         [InlineData(@"^[^<>]*(((?'Open'<)[^<>]*)+((?'Close-Open'>)[^<>]*)+)*(?(Open)(?!))$", RegexOptions.None, null)]