diff --git a/protobuf/protobuf2/Protobuf2.g4 b/protobuf/protobuf2/Protobuf2.g4
index 83892abb5b..253cc8b43a 100644
--- a/protobuf/protobuf2/Protobuf2.g4
+++ b/protobuf/protobuf2/Protobuf2.g4
@@ -132,7 +132,24 @@ type_
 // Extensions
 
 extensions
-    : EXTENSIONS ranges SEMI
+    : EXTENSIONS ranges (LB (verificationDef | declarations) RB)? SEMI
+    ;
+
+verificationDef
+    : VERIFICATION EQ verification
+    ;
+
+verification
+    : DECLARATION_LIT
+    | UNVERIFIED_LIT
+    ;
+
+declarations
+    : declaration (COMMA declaration)*
+    ;
+
+declaration
+    : DECLARATION EQ blockLit
     ;
 
 // Reserved
@@ -472,6 +489,22 @@ MAX
     : 'max'
     ;
 
+VERIFICATION
+    : 'verification'
+    ;
+
+DECLARATION
+    : 'declaration'
+    ;
+
+DECLARATION_LIT
+    : 'DECLARATION'
+    ;
+
+UNVERIFIED_LIT
+    : 'UNVERIFIED'
+    ;
+
 ENUM
     : 'enum'
     ;
@@ -707,4 +740,8 @@ keywords
     | STREAM
     | RETURNS
     | BOOL_LIT
+    | DECLARATION
+    | VERIFICATION
+    | DECLARATION_LIT
+    | UNVERIFIED_LIT
     ;
diff --git a/protobuf/protobuf2/examples/extension.proto b/protobuf/protobuf2/examples/extension.proto
new file mode 100644
index 0000000000..41b2936aa4
--- /dev/null
+++ b/protobuf/protobuf2/examples/extension.proto
@@ -0,0 +1,16 @@
+syntax = 'proto2';
+
+message UserContent {
+  extensions 100 to 199 [verification = DECLARATION];
+}
+
+message OtherContent {
+  extensions 100 to 199 [
+    declaration = {
+      number: 126,
+      full_name: ".kittens.kitten_videos",
+      type: ".kittens.Video",
+      repeated: true
+    }
+  ];
+}
\ No newline at end of file