diff --git a/cty/convert/conversion_collection.go b/cty/convert/conversion_collection.go
index 33c4df87..5b52d02d 100644
--- a/cty/convert/conversion_collection.go
+++ b/cty/convert/conversion_collection.go
@@ -39,6 +39,11 @@ func conversionCollectionToList(ety cty.Type, conv conversion) conversion {
 					return cty.NilVal, err
 				}
 			}
+
+			if val.IsNull() {
+				val = cty.NullVal(val.Type().WithoutOptionalAttributesDeep())
+			}
+
 			elems = append(elems, val)
 
 			i++
@@ -88,6 +93,11 @@ func conversionCollectionToSet(ety cty.Type, conv conversion) conversion {
 					return cty.NilVal, err
 				}
 			}
+
+			if val.IsNull() {
+				val = cty.NullVal(val.Type().WithoutOptionalAttributesDeep())
+			}
+
 			elems = append(elems, val)
 
 			i++
@@ -242,6 +252,11 @@ func conversionTupleToSet(tupleType cty.Type, setEty cty.Type, unsafe bool) conv
 					return cty.NilVal, err
 				}
 			}
+
+			if val.IsNull() {
+				val = cty.NullVal(val.Type().WithoutOptionalAttributesDeep())
+			}
+
 			elems = append(elems, val)
 
 			i++
@@ -524,6 +539,10 @@ func conversionMapToObject(mapType cty.Type, objType cty.Type, unsafe bool) conv
 				return cty.NilVal, path.NewErrorf("map element type is incompatible with attribute %q: %s", name.AsString(), MismatchMessage(val.Type(), objType.AttributeType(name.AsString())))
 			}
 
+			if val.IsNull() {
+				val = cty.NullVal(val.Type().WithoutOptionalAttributesDeep())
+			}
+
 			elems[name.AsString()] = val
 		}
 
diff --git a/cty/convert/public.go b/cty/convert/public.go
index af19bdc5..aab0d0ec 100644
--- a/cty/convert/public.go
+++ b/cty/convert/public.go
@@ -40,7 +40,7 @@ func GetConversionUnsafe(in cty.Type, out cty.Type) Conversion {
 // This is a convenience wrapper around calling GetConversionUnsafe and then
 // immediately passing the given value to the resulting function.
 func Convert(in cty.Value, want cty.Type) (cty.Value, error) {
-	if in.Type().Equals(want) {
+	if in.Type().Equals(want.WithoutOptionalAttributesDeep()) {
 		return in, nil
 	}
 
diff --git a/cty/convert/public_test.go b/cty/convert/public_test.go
index 602fc40c..a980fd35 100644
--- a/cty/convert/public_test.go
+++ b/cty/convert/public_test.go
@@ -1268,6 +1268,148 @@ func TestConvert(t *testing.T) {
 				})},
 			),
 		},
+		// We should strip optional attributes out of null values in sets, maps,
+		// lists and tuples.
+		{
+			Value: cty.ListVal([]cty.Value{
+				cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"})),
+			}),
+			Type: cty.Set(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+				"a": cty.String,
+			}, []string{"a"})),
+			Want: cty.SetVal([]cty.Value{
+				cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
+		{
+			Value: cty.TupleVal([]cty.Value{
+				cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"})),
+			}),
+			Type: cty.Set(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+				"a": cty.String,
+			}, []string{"a"})),
+			Want: cty.SetVal([]cty.Value{
+				cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
+		{
+			Value: cty.SetVal([]cty.Value{
+				cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"})),
+			}),
+			Type: cty.List(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+				"a": cty.String,
+			}, []string{"a"})),
+			Want: cty.ListVal([]cty.Value{
+				cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
+		{
+			Value: cty.TupleVal([]cty.Value{
+				cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"})),
+			}),
+			Type: cty.List(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+				"a": cty.String,
+			}, []string{"a"})),
+			Want: cty.ListVal([]cty.Value{
+				cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
+		{
+			Value: cty.ObjectVal(map[string]cty.Value{
+				"object": cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"})),
+			}),
+			Type: cty.Map(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+				"a": cty.String,
+			}, []string{"a"})),
+			Want: cty.MapVal(map[string]cty.Value{
+				"object": cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
+		{
+			Value: cty.MapVal(map[string]cty.Value{
+				"object": cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"})),
+			}),
+			Type: cty.Object(map[string]cty.Type{
+				"object": cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"}),
+			}),
+			Want: cty.ObjectVal(map[string]cty.Value{
+				"object": cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
+		{
+			Value: cty.MapVal(map[string]cty.Value{
+				"object": cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.Number,
+				}, []string{"a"})),
+			}),
+			Type: cty.Map(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+				"a": cty.String,
+			}, []string{"a"})),
+			Want: cty.MapVal(map[string]cty.Value{
+				"object": cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
+		{
+			Value: cty.TupleVal([]cty.Value{
+				cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.Number,
+				}, []string{"a"})),
+			}),
+			Type: cty.Tuple([]cty.Type{
+				cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"}),
+			}),
+			Want: cty.TupleVal([]cty.Value{
+				cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
+		// We should strip optional attributes out of types even if they match.
+		{
+			Value: cty.MapVal(map[string]cty.Value{
+				"object": cty.NullVal(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+					"a": cty.String,
+				}, []string{"a"})),
+			}),
+			Type: cty.Map(cty.ObjectWithOptionalAttrs(map[string]cty.Type{
+				"a": cty.String,
+			}, []string{"a"})),
+			Want: cty.MapVal(map[string]cty.Value{
+				"object": cty.NullVal(cty.Object(map[string]cty.Type{
+					"a": cty.String,
+				})),
+			}),
+		},
 	}
 
 	for _, test := range tests {