diff --git a/Cargo.toml b/Cargo.toml
index a77c1495a0..add9df033f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -35,9 +35,9 @@ utf8-ranges = "1.0.0"
 # For examples.
 lazy_static = "1"
 # For property based tests.
-quickcheck = { version = "0.5", default-features = false }
+quickcheck = { version = "0.6", default-features = false }
 # For generating random test data.
-rand = "0.3.15"
+rand = "0.4"
 
 [features]
 # Enable to use the unstable pattern traits defined in std.
diff --git a/regex-syntax/Cargo.toml b/regex-syntax/Cargo.toml
index 4ff62f546b..d3d0886ab7 100644
--- a/regex-syntax/Cargo.toml
+++ b/regex-syntax/Cargo.toml
@@ -9,5 +9,5 @@ homepage = "https://github.com/rust-lang/regex"
 description = "A regular expression parser."
 
 [dev-dependencies]
-quickcheck = { version = "0.5", default-features = false }
-rand = "0.3.15"
+quickcheck = { version = "0.6", default-features = false }
+rand = "0.4"