diff --git a/InterfaceStubGenerator.Shared/Parser.cs b/InterfaceStubGenerator.Shared/Parser.cs
index a603d7a6f..05a796d0c 100644
--- a/InterfaceStubGenerator.Shared/Parser.cs
+++ b/InterfaceStubGenerator.Shared/Parser.cs
@@ -34,6 +34,9 @@ CancellationToken cancellationToken
 
         refitInternalNamespace = $"{refitInternalNamespace ?? string.Empty}RefitInternalGenerated";
 
+        // Remove - as they are valid in csproj, but invalid in a namespace
+        refitInternalNamespace = refitInternalNamespace.Replace('-', '_');
+
         // we're going to create a new compilation that contains the attribute.
         // TODO: we should allow source generators to provide source during initialize, so that this step isn't required.
         var options = (CSharpParseOptions)compilation.SyntaxTrees[0].Options;