diff --git a/refinery_core/Cargo.toml b/refinery_core/Cargo.toml
index 810d0c67..aa438382 100644
--- a/refinery_core/Cargo.toml
+++ b/refinery_core/Cargo.toml
@@ -31,12 +31,12 @@ walkdir = "2.3.1"
 
 # allow multiple versions of the same dependency if API is similar
 rusqlite = { version = ">= 0.23, <= 0.29", optional = true }
-postgres = { version = "0.19", optional = true }
-tokio-postgres = { version = "0.7", optional = true }
+postgres = { version = ">=0.17, <= 0.19", optional = true }
+tokio-postgres = { version = ">= 0.5, <= 0.7", optional = true }
 mysql = { version = ">= 21.0.0, <= 23", optional = true, default-features = false }
 mysql_async = { version = ">= 0.28, <= 0.31", optional = true }
-tokio = { version = "1.0", features = ["full"], optional = true }
 tiberius = { version = ">= 0.7, <= 0.12", optional = true, default-features = false }
+tokio = { version = "1.0", features = ["full"], optional = true }
 futures = { version = "0.3.16", optional = true }
 tokio-util = { version = "0.7.7", features = ["compat"], optional = true }
 time = { version = "0.3.5", features = ["parsing", "formatting"] }