diff --git a/src/libraries/System.Private.CoreLib/src/System/Buffers/Text/Utf8Parser/Utf8Parser.Boolean.cs b/src/libraries/System.Private.CoreLib/src/System/Buffers/Text/Utf8Parser/Utf8Parser.Boolean.cs
index b19cee4e43ecc0..cb9af01b2327f3 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Buffers/Text/Utf8Parser/Utf8Parser.Boolean.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Buffers/Text/Utf8Parser/Utf8Parser.Boolean.cs
@@ -33,22 +33,44 @@ public static bool TryParse(ReadOnlySpan<byte> source, out bool value, out int b
 
             if (source.Length >= 4)
             {
-                int dw = BinaryPrimitives.ReadInt32LittleEndian(source) & ~0x20202020;
-                if (dw == 0x45555254 /* 'EURT' */)
+                int dw = BinaryPrimitives.ReadInt32LittleEndian(source);
+                if (standardFormat == default(char) || standardFormat == 'G')
                 {
-                    bytesConsumed = 4;
-                    value = true;
-                    return true;
-                }
+                    if (dw == 0x65757254 /* 'eurT' */)
+                    {
+                        bytesConsumed = 4;
+                        value = true;
+                        return true;
+                    }
 
-                if (source.Length > 4)
+                    if (source.Length > 4)
+                    {
+                        if (dw == 0x736C6146 /* 'slaF' */ && source[4] == 'e')
+                        {
+                            bytesConsumed = 5;
+                            value = false;
+                            return true;
+                        }
+                    }
+                }
+                else if (standardFormat == 'l')
                 {
-                    if (dw == 0x534c4146 /* 'SLAF' */ && (source[4] & ~0x20) == 'E')
+                    if (dw == 0x65757274 /* 'eurt' */)
                     {
-                        bytesConsumed = 5;
-                        value = false;
+                        bytesConsumed = 4;
+                        value = true;
                         return true;
                     }
+
+                    if (source.Length > 4)
+                    {
+                        if (dw == 0x736C6166 /* 'slaf' */ && source[4] == 'e')
+                        {
+                            bytesConsumed = 5;
+                            value = false;
+                            return true;
+                        }
+                    }
                 }
             }