diff --git a/Cargo.lock b/Cargo.lock
index f01cba9..94fddc6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -467,6 +467,7 @@ dependencies = [
  "hyper",
  "log 0.4.11",
  "prometheus",
+ "protobuf",
  "rocksdb",
  "rust-crypto",
  "serde",
@@ -1135,9 +1136,9 @@ dependencies = [
 
 [[package]]
 name = "protobuf"
-version = "2.18.0"
+version = "2.14.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6d147edb77bcccbfc81fabffdc7bd50c13e103b15ca1e27515fe40de69a5776b"
+checksum = "8e86d370532557ae7573551a1ec8235a0f8d6cb276c7c9e6aa490b511c447485"
 
 [[package]]
 name = "quick-error"
diff --git a/electrs_index/Cargo.toml b/electrs_index/Cargo.toml
index 895820c..ce93d53 100644
--- a/electrs_index/Cargo.toml
+++ b/electrs_index/Cargo.toml
@@ -14,7 +14,8 @@ env_logger = "0.7"
 hyper = "0.10"
 log = "0.4"
 prometheus = { version = "0.10", features = ["process"] }
-rocksdb = "^0.15.0"
+protobuf = "=2.14.0"  # due to https://github.com/stepancheg/rust-protobuf/blob/master/CHANGELOG.md#2150---2020-06-21
+rocksdb = "=0.15.0"
 rust-crypto = "0.2"
 serde = "1.0"
 serde_derive = "1.0"
diff --git a/rust-toolchain b/rust-toolchain
index 21998d3..f86fb9c 100644
--- a/rust-toolchain
+++ b/rust-toolchain
@@ -1 +1 @@
-1.47.0
+1.41.1