diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index c675af6803c..7eb96cbeb59 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -2436,7 +2436,8 @@ class parser {
                 !self.token_is_keyword(~"of", self.look_ahead(1)) &&
                 !self.token_is_keyword(~"for", self.look_ahead(1)) &&
                 self.look_ahead(1) != token::BINOP(token::SLASH) &&
-                self.look_ahead(1) != token::LT {
+                (self.look_ahead(1) != token::LT
+                 || (self.look_ahead(1) == token::LT && tps.is_not_empty())) {
 
             // This is a new-style impl declaration.
             ident = @~"__extensions__";     // XXX: clownshoes
diff --git a/src/test/run-pass/impl-implicit-trait.rs b/src/test/run-pass/impl-implicit-trait.rs
new file mode 100644
index 00000000000..e9ca583005c
--- /dev/null
+++ b/src/test/run-pass/impl-implicit-trait.rs
@@ -0,0 +1,20 @@
+enum option_<T> {
+    none_,
+    some_(T),
+}
+
+impl<T> option_<T> {
+    fn foo() -> bool { true }
+}
+
+enum option__ {
+    none__,
+    some__(int)
+}
+
+impl option__ {
+    fn foo() -> bool { true }
+}
+
+fn main() {
+}
\ No newline at end of file