diff --git a/crates/parser/src/grammar/generic_args.rs b/crates/parser/src/grammar/generic_args.rs
index c7d8040b24..b9d5bff663 100644
--- a/crates/parser/src/grammar/generic_args.rs
+++ b/crates/parser/src/grammar/generic_args.rs
@@ -45,7 +45,7 @@ pub(crate) const GENERIC_ARG_FIRST: TokenSet = TokenSet::new(&[
 const GENERIC_ARG_RECOVERY_SET: TokenSet = TokenSet::new(&[T![>], T![,]]);
 
 // test generic_arg
-// type T = S<i32>;
+// type T = S<i32, dyn T, fn()>;
 pub(crate) fn generic_arg(p: &mut Parser<'_>) -> bool {
     match p.current() {
         LIFETIME_IDENT if !p.nth_at(1, T![+]) => lifetime_arg(p),
@@ -57,6 +57,9 @@ pub(crate) fn generic_arg(p: &mut Parser<'_>) -> bool {
         // type ParenthesizedArgs = Foo<Item(T), Item::(T), Item(T): Bound, Item::(T): Bound, Item(T) = Item, Item::(T) = Item>;
         // type RTN = Foo<Item(..), Item(..), Item(..): Bound, Item(..): Bound, Item(..) = Item, Item(..) = Item>;
 
+        // test edition_2015_dyn_prefix_inside_generic_arg 2015
+        // type A = Foo<dyn T>;
+        T![ident] if !p.edition().at_least_2018() && types::is_dyn_weak(p) => type_arg(p),
         // test macro_inside_generic_arg
         // type A = Foo<syn::Token![_]>;
         k if PATH_NAME_REF_KINDS.contains(k) => {
diff --git a/crates/parser/src/grammar/types.rs b/crates/parser/src/grammar/types.rs
index 35198ccbe3..0133b7d5d8 100644
--- a/crates/parser/src/grammar/types.rs
+++ b/crates/parser/src/grammar/types.rs
@@ -58,7 +58,7 @@ fn type_with_bounds_cond(p: &mut Parser<'_>, allow_bounds: bool) {
     }
 }
 
-fn is_dyn_weak(p: &Parser<'_>) -> bool {
+pub(crate) fn is_dyn_weak(p: &Parser<'_>) -> bool {
     const WEAK_DYN_PATH_FIRST: TokenSet = TokenSet::new(&[
         IDENT,
         T![self],
diff --git a/crates/parser/test_data/generated/runner.rs b/crates/parser/test_data/generated/runner.rs
index f9486f53c2..0beaf1ae3a 100644
--- a/crates/parser/test_data/generated/runner.rs
+++ b/crates/parser/test_data/generated/runner.rs
@@ -190,6 +190,13 @@ mod ok {
         );
     }
     #[test]
+    fn edition_2015_dyn_prefix_inside_generic_arg() {
+        run_and_expect_no_errors_with_edition(
+            "test_data/parser/inline/ok/edition_2015_dyn_prefix_inside_generic_arg.rs",
+            crate::Edition::Edition2015,
+        );
+    }
+    #[test]
     fn effect_blocks() { run_and_expect_no_errors("test_data/parser/inline/ok/effect_blocks.rs"); }
     #[test]
     fn exclusive_range_pat() {
diff --git a/crates/parser/test_data/parser/inline/ok/edition_2015_dyn_prefix_inside_generic_arg.rast b/crates/parser/test_data/parser/inline/ok/edition_2015_dyn_prefix_inside_generic_arg.rast
new file mode 100644
index 0000000000..24e671b343
--- /dev/null
+++ b/crates/parser/test_data/parser/inline/ok/edition_2015_dyn_prefix_inside_generic_arg.rast
@@ -0,0 +1,32 @@
+SOURCE_FILE
+  TYPE_ALIAS
+    COMMENT "// 2015"
+    WHITESPACE "\n"
+    TYPE_KW "type"
+    WHITESPACE " "
+    NAME
+      IDENT "A"
+    WHITESPACE " "
+    EQ "="
+    WHITESPACE " "
+    PATH_TYPE
+      PATH
+        PATH_SEGMENT
+          NAME_REF
+            IDENT "Foo"
+          GENERIC_ARG_LIST
+            L_ANGLE "<"
+            TYPE_ARG
+              DYN_TRAIT_TYPE
+                DYN_KW "dyn"
+                WHITESPACE " "
+                TYPE_BOUND_LIST
+                  TYPE_BOUND
+                    PATH_TYPE
+                      PATH
+                        PATH_SEGMENT
+                          NAME_REF
+                            IDENT "T"
+            R_ANGLE ">"
+    SEMICOLON ";"
+  WHITESPACE "\n"
diff --git a/crates/parser/test_data/parser/inline/ok/edition_2015_dyn_prefix_inside_generic_arg.rs b/crates/parser/test_data/parser/inline/ok/edition_2015_dyn_prefix_inside_generic_arg.rs
new file mode 100644
index 0000000000..84cece5748
--- /dev/null
+++ b/crates/parser/test_data/parser/inline/ok/edition_2015_dyn_prefix_inside_generic_arg.rs
@@ -0,0 +1,2 @@
+// 2015
+type A = Foo<dyn T>;
diff --git a/crates/parser/test_data/parser/inline/ok/generic_arg.rast b/crates/parser/test_data/parser/inline/ok/generic_arg.rast
index 5a01f154ba..e32cf08565 100644
--- a/crates/parser/test_data/parser/inline/ok/generic_arg.rast
+++ b/crates/parser/test_data/parser/inline/ok/generic_arg.rast
@@ -20,6 +20,27 @@ SOURCE_FILE
                   PATH_SEGMENT
                     NAME_REF
                       IDENT "i32"
+            COMMA ","
+            WHITESPACE " "
+            TYPE_ARG
+              DYN_TRAIT_TYPE
+                DYN_KW "dyn"
+                WHITESPACE " "
+                TYPE_BOUND_LIST
+                  TYPE_BOUND
+                    PATH_TYPE
+                      PATH
+                        PATH_SEGMENT
+                          NAME_REF
+                            IDENT "T"
+            COMMA ","
+            WHITESPACE " "
+            TYPE_ARG
+              FN_PTR_TYPE
+                FN_KW "fn"
+                PARAM_LIST
+                  L_PAREN "("
+                  R_PAREN ")"
             R_ANGLE ">"
     SEMICOLON ";"
   WHITESPACE "\n"
diff --git a/crates/parser/test_data/parser/inline/ok/generic_arg.rs b/crates/parser/test_data/parser/inline/ok/generic_arg.rs
index f2ccc558bb..cf991b5b36 100644
--- a/crates/parser/test_data/parser/inline/ok/generic_arg.rs
+++ b/crates/parser/test_data/parser/inline/ok/generic_arg.rs
@@ -1 +1 @@
-type T = S<i32>;
+type T = S<i32, dyn T, fn()>;