diff --git a/extensions/default_unparsing_config.json b/extensions/default_unparsing_config.json
index 5edf4c471..933cf3df8 100644
--- a/extensions/default_unparsing_config.json
+++ b/extensions/default_unparsing_config.json
@@ -2294,6 +2294,13 @@
         ]
       }
     },
+    "ExprAlternativesList": {
+      "sep": [
+        "line",
+        "recurse",
+        "whitespace"
+      ]
+    },
     "ExprFunction": {
       "node": {
         "kind": "group",
@@ -3616,6 +3623,55 @@
         ]
       }
     },
+    "MembershipExpr": {
+      "node": {
+        "kind": "innerRoot",
+        "contents": {
+          "kind": "group",
+          "document": [
+            {
+              "kind": "group",
+              "document": [
+                {
+                  "kind": "recurse_field",
+                  "field": "f_expr"
+                },
+                "line",
+                {
+                  "kind": "recurse_field",
+                  "field": "f_op"
+                }
+              ],
+              "id": "expr_with_op"
+            },
+            {
+              "kind": "ifBreak",
+              "flatContents": {
+                "kind": "continuationLineIndent",
+                "contents": [
+                  "line",
+                  {
+                    "kind": "recurse_field",
+                    "field": "f_membership_exprs"
+                  }
+                ]
+              },
+              "breakContents": [
+                "whitespace",
+                {
+                  "kind": "innerRoot",
+                  "contents": {
+                    "kind": "recurse_field",
+                    "field": "f_membership_exprs"
+                  }
+                }
+              ],
+              "groupId": "expr_with_op"
+            }
+          ]
+        }
+      }
+    },
     "ModeIn": {
       "node": [
         {
diff --git a/testsuite/tests/unparsing/membership_expr/f_op_in/input.ada b/testsuite/tests/unparsing/membership_expr/f_op_in/input.ada
new file mode 100644
index 000000000..ae5b84b85
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/f_op_in/input.ada
@@ -0,0 +1,40 @@
+function Is_Expected_Parent_Kind (Kiiiiiind : Ada_Node_Kind_Type) return Boolean
+is (Kiiiiiiiiind.Something_That_Is_Veeeeeeeeeeeeeeeeeeeeeeery_Looooooooooooooong
+    in Ada_Package_Body
+       | Ada_Package_Decl
+       | Ada_Library_Item
+       | Ada_Subp_Body
+       | Ada_Task_Body
+       | Ada_Decl_Block
+       | Ada_For_Loop_Stmt
+       | Ada_Loop_Stmt
+       | Ada_While_Loop_Stmt
+       | Ada_If_Stmt_Range
+       | Ada_Case_Stmt_Range
+       | Ada_Case_Stmt_Alternative_Range
+    and Kiiiiiiiiind.Something_That_Is_Veeeeeeeeeeeeeeeeeeeeeeery_Looooooooooooooong.Foooooooooooooooo in
+          Ada_Package_Body
+          | Ada_Package_Decl
+          | Ada_Library_Item
+          | Ada_Subp_Body
+          | Ada_Task_Body
+          | Ada_Decl_Block
+          | Ada_For_Loop_Stmt
+          | Ada_Loop_Stmt
+          | Ada_While_Loop_Stmt
+          | Ada_If_Stmt_Range
+          | Ada_Case_Stmt_Range
+          | Ada_Case_Stmt_Alternative_Range
+    and Kiiiiiiiiind in
+          Ada_Package_Body
+          | Ada_Package_Decl
+          | Ada_Library_Item
+          | Ada_Subp_Body
+          | Ada_Task_Body
+          | Ada_Decl_Block
+          | Ada_For_Loop_Stmt
+          | Ada_Loop_Stmt
+          | Ada_While_Loop_Stmt
+          | Ada_If_Stmt_Range
+          | Ada_Case_Stmt_Range
+          | Ada_Case_Stmt_Alternative_Range);
diff --git a/testsuite/tests/unparsing/membership_expr/f_op_in/test.out b/testsuite/tests/unparsing/membership_expr/f_op_in/test.out
new file mode 100644
index 000000000..fdc0709d8
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/f_op_in/test.out
@@ -0,0 +1,44 @@
+function Is_Expected_Parent_Kind
+  (Kiiiiiind : Ada_Node_Kind_Type) return Boolean
+is (Kiiiiiiiiind
+      .Something_That_Is_Veeeeeeeeeeeeeeeeeeeeeeery_Looooooooooooooong
+    in Ada_Package_Body
+       | Ada_Package_Decl
+       | Ada_Library_Item
+       | Ada_Subp_Body
+       | Ada_Task_Body
+       | Ada_Decl_Block
+       | Ada_For_Loop_Stmt
+       | Ada_Loop_Stmt
+       | Ada_While_Loop_Stmt
+       | Ada_If_Stmt_Range
+       | Ada_Case_Stmt_Range
+       | Ada_Case_Stmt_Alternative_Range
+    and Kiiiiiiiiind
+          .Something_That_Is_Veeeeeeeeeeeeeeeeeeeeeeery_Looooooooooooooong
+          .Foooooooooooooooo
+        in Ada_Package_Body
+           | Ada_Package_Decl
+           | Ada_Library_Item
+           | Ada_Subp_Body
+           | Ada_Task_Body
+           | Ada_Decl_Block
+           | Ada_For_Loop_Stmt
+           | Ada_Loop_Stmt
+           | Ada_While_Loop_Stmt
+           | Ada_If_Stmt_Range
+           | Ada_Case_Stmt_Range
+           | Ada_Case_Stmt_Alternative_Range
+    and Kiiiiiiiiind in
+          Ada_Package_Body
+          | Ada_Package_Decl
+          | Ada_Library_Item
+          | Ada_Subp_Body
+          | Ada_Task_Body
+          | Ada_Decl_Block
+          | Ada_For_Loop_Stmt
+          | Ada_Loop_Stmt
+          | Ada_While_Loop_Stmt
+          | Ada_If_Stmt_Range
+          | Ada_Case_Stmt_Range
+          | Ada_Case_Stmt_Alternative_Range);
diff --git a/testsuite/tests/unparsing/membership_expr/f_op_in/test.yaml b/testsuite/tests/unparsing/membership_expr/f_op_in/test.yaml
new file mode 100644
index 000000000..691bd9f95
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/f_op_in/test.yaml
@@ -0,0 +1,5 @@
+driver: unparser
+rule: subp_decl
+description: |
+  Test that the `f_membership_exprs` field is correctly indented based on
+  `f_expr` when `f_op` is an `OpIn` node.
diff --git a/testsuite/tests/unparsing/membership_expr/f_op_not_in/input.ada b/testsuite/tests/unparsing/membership_expr/f_op_not_in/input.ada
new file mode 100644
index 000000000..59ef7c1ff
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/f_op_not_in/input.ada
@@ -0,0 +1,10 @@
+procedure Foo
+is
+begin
+   if Parent.Parent.Kind not in Ada_Begin_Block_Range | Ada_Decl_Block_Range | Bar
+     and then Parent_Parent.Parent_Parent.Parent_Parent.Parent_Kind not in Ada_Begin_Block_Range | Ada_Decl_Block_Range | Bar
+     and then Parent_Parent.Parent_Parent.Parent_Parent.Parent_Parent.Parent_Kind not in Ada_Begin_Block_Range | Ada_Decl_Block_Range | Bar
+   then
+      Current_Indentation := @ + Indentation;
+   end if;
+end Foo;
diff --git a/testsuite/tests/unparsing/membership_expr/f_op_not_in/test.out b/testsuite/tests/unparsing/membership_expr/f_op_not_in/test.out
new file mode 100644
index 000000000..bea2e0541
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/f_op_not_in/test.out
@@ -0,0 +1,22 @@
+procedure Foo is
+begin
+   if Parent.Parent.Kind not in
+        Ada_Begin_Block_Range
+        | Ada_Decl_Block_Range
+        | Bar
+     and then Parent_Parent.Parent_Parent.Parent_Parent.Parent_Kind not in
+                Ada_Begin_Block_Range
+                | Ada_Decl_Block_Range
+                | Bar
+     and then Parent_Parent
+                .Parent_Parent
+                .Parent_Parent
+                .Parent_Parent
+                .Parent_Kind
+              not in Ada_Begin_Block_Range
+                     | Ada_Decl_Block_Range
+                     | Bar
+   then
+      Current_Indentation := @ + Indentation;
+   end if;
+end Foo;
diff --git a/testsuite/tests/unparsing/membership_expr/f_op_not_in/test.yaml b/testsuite/tests/unparsing/membership_expr/f_op_not_in/test.yaml
new file mode 100644
index 000000000..bbd389ab7
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/f_op_not_in/test.yaml
@@ -0,0 +1,5 @@
+driver: unparser
+rule: subp_body
+description: |
+  Test that the `f_membership_exprs` field is correctly indented based on
+  `f_expr` when `f_op` is an `OpNotIn` node.
diff --git a/testsuite/tests/unparsing/membership_expr/short/input.ada b/testsuite/tests/unparsing/membership_expr/short/input.ada
new file mode 100644
index 000000000..adf50c754
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/short/input.ada
@@ -0,0 +1,2 @@
+function Is_Expected_Parent_Kind (Kind_1, Kind_2: Ada_Node_Kind_Type) return Boolean
+is (Kind_1 in Ada_Package_Body and Kind_2 in Ada_Subp_Body);
diff --git a/testsuite/tests/unparsing/membership_expr/short/test.out b/testsuite/tests/unparsing/membership_expr/short/test.out
new file mode 100644
index 000000000..c3c515332
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/short/test.out
@@ -0,0 +1,3 @@
+function Is_Expected_Parent_Kind
+  (Kind_1, Kind_2 : Ada_Node_Kind_Type) return Boolean
+is (Kind_1 in Ada_Package_Body and Kind_2 in Ada_Subp_Body);
diff --git a/testsuite/tests/unparsing/membership_expr/short/test.yaml b/testsuite/tests/unparsing/membership_expr/short/test.yaml
new file mode 100644
index 000000000..cb0336d9e
--- /dev/null
+++ b/testsuite/tests/unparsing/membership_expr/short/test.yaml
@@ -0,0 +1,4 @@
+driver: unparser
+rule: expr_fn
+description: |
+  Test that no line breaks are added when `MembershipExpr`s fits on the line.