1 files changed, 10 insertions, 1 deletions
diff --git a/source/slang/slang-check-expr.cpp b/source/slang/slang-check-expr.cpp
index a52a08f15..7e2bc3822 100644
--- a/source/slang/slang-check-expr.cpp
+++ b/source/slang/slang-check-expr.cpp
@@ -2232,9 +2232,18 @@ namespace Slang
             {
                 if (as<DifferentialPairType>(derivType))
                 {
-                    // Using inout type on all the derivative parameters
+                    // An `in` differentiable parameter becomes an `inout` parameter.
                     derivType = m_astBuilder->getInOutType(derivType);
                 }
+                else if (auto inoutType = as<InOutType>(derivType))
+                {
+                    if (!as<DifferentialPairType>(inoutType->getValueType()))
+                    {
+                        // An `inout` non differentiable parameter becomes an `in` parameter
+                        // (removing `out`).
+                        derivType = inoutType->getValueType();
+                    }
+                }
                 type->paramTypes.add(derivType);
             }
         }