diff --git a/src/Hl7.Fhir.Base/FhirPath/Expressions/EchoVisitor.cs b/src/Hl7.Fhir.Base/FhirPath/Expressions/EchoVisitor.cs
index c52527209f..f86665b418 100644
--- a/src/Hl7.Fhir.Base/FhirPath/Expressions/EchoVisitor.cs
+++ b/src/Hl7.Fhir.Base/FhirPath/Expressions/EchoVisitor.cs
@@ -5,6 +5,8 @@
  * This file is licensed under the BSD 3-Clause license
  * available at https://raw.githubusercontent.com/FirelyTeam/firely-net-sdk/master/LICENSE
  */
+
+using System.Globalization;
 using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -113,7 +115,7 @@ public override StringBuilder VisitConstant(ConstantExpression expression)
                 case "Quantity":
                     if (expression.Value is P.Quantity q)
                     {
-                        _result.Append($"{q?.Value}");
+                        _result.Append(q.Value.ToString(CultureInfo.InvariantCulture));
                         OutputSubToken(expression.Unit);
                     }
                     else
@@ -298,4 +300,4 @@ public static string EchoExpression(this Expression expr)
         }
     }
 
-}
+}
\ No newline at end of file
diff --git a/src/Hl7.Fhir.Base/FhirPath/Parser/Grammar.cs b/src/Hl7.Fhir.Base/FhirPath/Parser/Grammar.cs
index 7b317b3f2e..a019b18eed 100644
--- a/src/Hl7.Fhir.Base/FhirPath/Parser/Grammar.cs
+++ b/src/Hl7.Fhir.Base/FhirPath/Parser/Grammar.cs
@@ -11,6 +11,7 @@
 using Hl7.FhirPath.Sprache;
 using P = Hl7.Fhir.ElementModel.Types;
 using System;
+using System.Globalization;
 using System.Linq;
 
 namespace Hl7.FhirPath.Parser
@@ -24,7 +25,8 @@ private static IResult<ConstantExpression> quantityParser(IInput i)
             // Note that quantities are always parsed with a unit, otherwise they would be an integer or decimal
             // and the +/- are unary operators and not a part of the quantity itself.
             var result = (
-                from val in Lexer.DecimalNumber.Select(n => $"{n}").Or(Lexer.IntegerNumber.Select(n => $"{n}")).Select(v => new SubToken(v)).Positioned()
+                from val in Lexer.DecimalNumber.Select(n => n.ToString(CultureInfo.InvariantCulture))
+                    .Or(Lexer.IntegerNumber.Select(n => n.ToString(CultureInfo.InvariantCulture))).Select(v => new SubToken(v)).Positioned()
                 from ws in WhitespaceOrComments()
                 from unit in Lexer.String.Select(u => $"'{u.Replace("'", "\\'")}'").Or(Lexer.Id).Select(v => new SubToken(v).WithLeadingWS(ws)).Positioned()
                 select (valToken: val, unitToken: unit)
@@ -319,4 +321,4 @@ from wsTrailing in WhitespaceOrComments()
             .Many()
             .Named("Whitespace and/or comments");
     }
-}
+}
\ No newline at end of file