diff --git a/src/dmd/parse.d b/src/dmd/parse.d
index 16e430f94f7a..c0192f6de741 100644
--- a/src/dmd/parse.d
+++ b/src/dmd/parse.d
@@ -2864,7 +2864,8 @@ final class Parser(AST) : Lexer
                         // Don't call nextToken again.
                     }
                 case TOK.in_:
-                    stc = STC.in_;
+                    // `in` now means `const scope` as originally intented
+                    stc = STC.const_ | STC.scope_;
                     goto L2;
 
                 case TOK.out_:
diff --git a/src/dmd/semantic3.d b/src/dmd/semantic3.d
index 1b7fa139014f..3e594aa341ae 100644
--- a/src/dmd/semantic3.d
+++ b/src/dmd/semantic3.d
@@ -456,8 +456,14 @@ private extern(C++) final class Semantic3Visitor : Visitor
                             stc |= STC.scope_;
                         }
                     }
-                    if (funcdecl.flags & FUNCFLAG.inferScope && !(fparam.storageClass & STC.scope_))
+
+                    // infer scope for lambdas even without -preview=dip1000
+                    // See https://issues.dlang.org/show_bug.cgi?id=20362
+                    const isLambda = funcdecl.isFuncLiteralDeclaration;
+
+                    if ((funcdecl.flags & FUNCFLAG.inferScope || isLambda) && !(fparam.storageClass & STC.scope_))
                         stc |= STC.maybescope;
+
                     stc |= fparam.storageClass & (STC.in_ | STC.out_ | STC.ref_ | STC.return_ | STC.scope_ | STC.lazy_ | STC.final_ | STC.TYPECTOR | STC.nodtor);
                     v.storage_class = stc;
                     v.dsymbolSemantic(sc2);
diff --git a/test/compilable/extra-files/header2.di b/test/compilable/extra-files/header2.di
index 9f469b51a55f..b46460f30e71 100644
--- a/test/compilable/extra-files/header2.di
+++ b/test/compilable/extra-files/header2.di
@@ -2,7 +2,7 @@ class C
 {
 }
 void foo(const C c, const(char)[] s, const int* q, const(int*) p);
-void bar(in void* p);
+void bar(scope const void* p);
 void f(void function() f2);
 class C2;
 void foo2(const C2 c);
@@ -93,7 +93,7 @@ void foo11217()(auto ref int[] arr)
 void foo11217()(scope int[] arr)
 {
 }
-void foo11217()(in int[] arr)
+void foo11217()(scope const int[] arr)
 {
 }
 void foo11217()(inout int[] arr)
diff --git a/test/compilable/extra-files/header2i.di b/test/compilable/extra-files/header2i.di
index a8a1db04a7d9..d6672b89360f 100644
--- a/test/compilable/extra-files/header2i.di
+++ b/test/compilable/extra-files/header2i.di
@@ -4,7 +4,7 @@ class C
 void foo(const C c, const(char)[] s, const int* q, const(int*) p)
 {
 }
-void bar(in void* p)
+void bar(scope const void* p)
 {
 }
 void f(void function() f2);
@@ -106,7 +106,7 @@ void foo11217()(auto ref int[] arr)
 void foo11217()(scope int[] arr)
 {
 }
-void foo11217()(in int[] arr)
+void foo11217()(scope const int[] arr)
 {
 }
 void foo11217()(inout int[] arr)
diff --git a/test/compilable/test_in_scope_const.d b/test/compilable/test_in_scope_const.d
new file mode 100644
index 000000000000..ec17c202481d
--- /dev/null
+++ b/test/compilable/test_in_scope_const.d
@@ -0,0 +1,13 @@
+/* REQUIRED_ARGS: -preview=dip1000
+ */
+
+@safe:
+
+import std.traits: ParameterStorageClassTuple, ParameterStorageClass, Parameters;
+
+void fun(in int* inParam);
+alias storages = ParameterStorageClassTuple!fun;
+alias storage = storages[0];
+
+static assert(is(Parameters!fun[0] == const int*));
+static assert(storage & ParameterStorageClass.scope_);
diff --git a/test/fail_compilation/fail183.d b/test/fail_compilation/fail183.d
index c43d377e9f92..c72a6d300503 100644
--- a/test/fail_compilation/fail183.d
+++ b/test/fail_compilation/fail183.d
@@ -3,7 +3,7 @@ TEST_OUTPUT:
 ---
 fail_compilation/fail183.d(10): Error: redundant attribute `const`
 fail_compilation/fail183.d(10): Error: redundant attribute `scope`
-fail_compilation/fail183.d(11): Error: redundant attribute `in`
+fail_compilation/fail183.d(11): Error: redundant attribute `scope const`
 ---
 */