diff --git a/crates/ra_syntax/src/grammar/params.rs b/crates/ra_syntax/src/grammar/params.rs
index 658fc582098..13158429a94 100644
--- a/crates/ra_syntax/src/grammar/params.rs
+++ b/crates/ra_syntax/src/grammar/params.rs
@@ -79,7 +79,12 @@ fn value_parameter(p: &mut Parser, flavor: Flavor) {
             let la1 = p.nth(1);
             let la2 = p.nth(2);
             let la3 = p.nth(3);
-            if la0 == IDENT && la1 == COLON
+
+            // test trait_fn_placeholder_parameter
+            // trait Foo {
+            //     fn bar(_: u64);
+            // }
+            if (la0 == IDENT || la0 == UNDERSCORE) && la1 == COLON
                 || la0 == AMP && la1 == IDENT && la2 == COLON
                 || la0 == AMP && la1 == MUT_KW && la2 == IDENT && la3 == COLON
             {
diff --git a/crates/ra_syntax/tests/data/parser/inline/ok/0116_trait_fn_placeholder_parameter.rs b/crates/ra_syntax/tests/data/parser/inline/ok/0116_trait_fn_placeholder_parameter.rs
new file mode 100644
index 00000000000..aede3f4febb
--- /dev/null
+++ b/crates/ra_syntax/tests/data/parser/inline/ok/0116_trait_fn_placeholder_parameter.rs
@@ -0,0 +1,3 @@
+trait Foo {
+    fn bar(_: u64);
+}
diff --git a/crates/ra_syntax/tests/data/parser/inline/ok/0116_trait_fn_placeholder_parameter.txt b/crates/ra_syntax/tests/data/parser/inline/ok/0116_trait_fn_placeholder_parameter.txt
new file mode 100644
index 00000000000..248d491dfee
--- /dev/null
+++ b/crates/ra_syntax/tests/data/parser/inline/ok/0116_trait_fn_placeholder_parameter.txt
@@ -0,0 +1,32 @@
+SOURCE_FILE@[0; 34)
+  TRAIT_DEF@[0; 33)
+    TRAIT_KW@[0; 5)
+    WHITESPACE@[5; 6)
+    NAME@[6; 9)
+      IDENT@[6; 9) "Foo"
+    WHITESPACE@[9; 10)
+    ITEM_LIST@[10; 33)
+      L_CURLY@[10; 11)
+      WHITESPACE@[11; 16)
+      FN_DEF@[16; 31)
+        FN_KW@[16; 18)
+        WHITESPACE@[18; 19)
+        NAME@[19; 22)
+          IDENT@[19; 22) "bar"
+        PARAM_LIST@[22; 30)
+          L_PAREN@[22; 23)
+          PARAM@[23; 29)
+            PLACEHOLDER_PAT@[23; 24)
+              UNDERSCORE@[23; 24)
+            COLON@[24; 25)
+            WHITESPACE@[25; 26)
+            PATH_TYPE@[26; 29)
+              PATH@[26; 29)
+                PATH_SEGMENT@[26; 29)
+                  NAME_REF@[26; 29)
+                    IDENT@[26; 29) "u64"
+          R_PAREN@[29; 30)
+        SEMI@[30; 31)
+      WHITESPACE@[31; 32)
+      R_CURLY@[32; 33)
+  WHITESPACE@[33; 34)