diff --git a/src/Fantomas.Tests/SignatureTests.fs b/src/Fantomas.Tests/SignatureTests.fs
index 8542310873..611d0efd47 100644
--- a/src/Fantomas.Tests/SignatureTests.fs
+++ b/src/Fantomas.Tests/SignatureTests.fs
@@ -1105,3 +1105,49 @@ module Teq =
         val domainOf<'domain1, 'domain2, 'range1, 'range2> :
             Teq<'domain1 -> 'range1, 'domain2 -> 'range2> -> Teq<'domain1, 'domain2>
 """
+
+[<Test>]
+let ``inline type definition member, 1399`` () =
+    formatSourceString
+        true
+        """
+namespace Baz
+
+[<Sealed>]
+type Foo =
+    member inline Return : 'a -> Baz<'a>
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+namespace Baz
+
+[<Sealed>]
+type Foo =
+    member inline Return: 'a -> Baz<'a>
+"""
+
+[<Test>]
+let ``inline private type definition member`` () =
+    formatSourceString
+        true
+        """
+namespace Baz
+
+[<Sealed>]
+type Foo =
+    member inline private Return : 'a -> Baz<'a>
+"""
+        config
+    |> prepend newline
+    |> should
+        equal
+        """
+namespace Baz
+
+[<Sealed>]
+type Foo =
+    member inline private Return: 'a -> Baz<'a>
+"""
diff --git a/src/Fantomas/CodePrinter.fs b/src/Fantomas/CodePrinter.fs
index 653c5c20e1..b52ae8bb57 100644
--- a/src/Fantomas/CodePrinter.fs
+++ b/src/Fantomas/CodePrinter.fs
@@ -3714,7 +3714,7 @@ and genMemberSig astContext node =
         | SynMemberSig.NestedType (_, r) -> r, SynMemberSig_NestedType
 
     match node with
-    | MSMember (Val (ats, px, ao, s, t, vi, _, ValTyparDecls (tds, _, tcs)), mf) ->
+    | MSMember (Val (ats, px, ao, s, t, vi, isInline, ValTyparDecls (tds, _, tcs)), mf) ->
         let (FunType namedArgs) = (t, vi)
 
         let isFunctionProperty =
@@ -3735,6 +3735,7 @@ and genMemberSig astContext node =
                       InterfaceRange = None }
                 mf
                 range
+            +> ifElse isInline (!- "inline ") sepNone
             +> opt sepSpace ao genAccess
             +> ifElse (s = "``new``") (!- "new") (!-s)
             +> genTypeParamPostfix astContext tds tcs