diff --git a/benchmark/benchmark.py b/benchmark/benchmark.py
index 1c77ad281..989647080 100644
--- a/benchmark/benchmark.py
+++ b/benchmark/benchmark.py
@@ -134,6 +134,7 @@ def iterate(seq: Any) -> None:
         ("${a:b,c,d}", ValueKind.INTERPOLATION),
         ("${${b}}", ValueKind.INTERPOLATION),
         ("${a:${b}}", ValueKind.INTERPOLATION),
+        ("${foooooooooooooooooooo}_${bar}", ValueKind.INTERPOLATION),
     ],
 )
 def test_get_value_kind(
diff --git a/omegaconf/grammar_parser.py b/omegaconf/grammar_parser.py
index 181e702c9..9d660618f 100644
--- a/omegaconf/grammar_parser.py
+++ b/omegaconf/grammar_parser.py
@@ -18,10 +18,10 @@
 
 # Build regex pattern to efficiently identify typical interpolations.
 # See test `test_match_simple_interpolation_pattern` for examples.
-_id = "[a-zA-Z_]\\w*"  # foo, foo_bar, abc123
-_config_key = f"({_id}|\\$)+"  # foo, $bar, $foo$bar$
+_config_key = r"[$\w]+"  # foo, $0, $bar, $foo_$bar123$
 _node_path = f"(\\.)*({_config_key}(\\.{_config_key})*)?"  # foo, .foo.$bar
 _node_inter = f"\\${{\\s*{_node_path}\\s*}}"  # node interpolation ${foo.bar}
+_id = "[a-zA-Z_]\\w*"  # foo, foo_bar, abc123
 _resolver_name = f"({_id}(\\.{_id})*)?"  # foo, ns.bar3, ns_1.ns_2.b0z
 _arg = "[a-zA-Z_0-9/\\-\\+.$%*@]+"  # string representing a resolver argument
 _args = f"{_arg}(\\s*,\\s*{_arg})*"  # list of resolver arguments
diff --git a/tests/test_grammar.py b/tests/test_grammar.py
index 963b9b11d..b46e5df18 100644
--- a/tests/test_grammar.py
+++ b/tests/test_grammar.py
@@ -531,6 +531,8 @@ def visit() -> Any:
         "\\${foo}",
         "${foo.bar:boz}",
         "${$foo.bar$.x$y}",
+        "${$0.1.2$}",
+        "${0foo}",
         # relative interpolations
         "${.}",
         "${..}",
@@ -548,7 +550,6 @@ def test_match_simple_interpolation_pattern(expression: str) -> None:
     "expression",
     [
         "${foo",
-        "${0foo}",
         "${0foo:bar}",
         "${foo.${bar}}",
         "${foo:${bar}}",