diff --git a/Cargo.lock b/Cargo.lock
index 2a42d0877..4da9f300f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -121,6 +121,7 @@ name = "base64ct"
 version = "1.6.0"
 dependencies = [
  "base64",
+ "clap",
  "proptest",
 ]
 
@@ -1052,9 +1053,9 @@ dependencies = [
 
 [[package]]
 name = "proptest"
-version = "1.4.0"
+version = "1.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "31b476131c3c86cb68032fdc5cb6d5a1045e3e42d96b69fa599fd77701e1f5bf"
+checksum = "7c003ac8c77cb07bb74f5f198bce836a689bcd5a42574612bf14d17bfd08c20e"
 dependencies = [
  "bit-set",
  "bit-vec",
@@ -1064,7 +1065,7 @@ dependencies = [
  "rand",
  "rand_chacha",
  "rand_xorshift",
- "regex-syntax",
+ "regex-syntax 0.7.5",
  "rusty-fork",
  "tempfile",
  "unarray",
@@ -1142,7 +1143,7 @@ dependencies = [
  "aho-corasick",
  "memchr",
  "regex-automata",
- "regex-syntax",
+ "regex-syntax 0.8.2",
 ]
 
 [[package]]
@@ -1153,9 +1154,15 @@ checksum = "5f804c7828047e88b2d32e2d7fe5a105da8ee3264f01902f796c8e067dc2483f"
 dependencies = [
  "aho-corasick",
  "memchr",
- "regex-syntax",
+ "regex-syntax 0.8.2",
 ]
 
+[[package]]
+name = "regex-syntax"
+version = "0.7.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dbb5fb1acd8a1a18b3dd5be62d25485eb770e05afb408a9627d14d451bae12da"
+
 [[package]]
 name = "regex-syntax"
 version = "0.8.2"
diff --git a/base32ct/Cargo.toml b/base32ct/Cargo.toml
index b71a629ab..2d8e71fd5 100644
--- a/base32ct/Cargo.toml
+++ b/base32ct/Cargo.toml
@@ -18,7 +18,8 @@ rust-version = "1.60"
 
 [dev-dependencies]
 base32 = "0.4"
-proptest = "1"
+# pinned to preserve MSRV
+proptest = { version = "=1.3.1", default-features = false, features = ["std"] }
 
 [features]
 alloc = []
diff --git a/base64ct/Cargo.toml b/base64ct/Cargo.toml
index faea9ec19..1cbf41bf9 100644
--- a/base64ct/Cargo.toml
+++ b/base64ct/Cargo.toml
@@ -18,7 +18,9 @@ rust-version = "1.60"
 
 [dev-dependencies]
 base64 = "0.21"
-proptest = { version = "1", default-features = false, features = ["std"] }
+clap = "=4.3.23"
+# pinned to preserve MSRV
+proptest = { version = "=1.3.1", default-features = false, features = ["std"] }
 
 [features]
 alloc = []