diff --git a/base32ct/tests/proptests.rs b/base32ct/tests/proptests.rs
index aa0a36d2d..89f1ebb7f 100644
--- a/base32ct/tests/proptests.rs
+++ b/base32ct/tests/proptests.rs
@@ -34,4 +34,35 @@ proptest! {
         let expected = base32::encode(RFC4648_PADDED, &bytes).to_lowercase();
         prop_assert_eq!(actual, expected);
     }
+
+    /// Make sure that, if base32ct and base32 _both_ decode a value
+    /// when expecting padded inputs, they give the same output.
+    ///
+    /// TODO: It might be desirable to ensure that they both decode the
+    /// _same_ values: that is, that they are equivalently strict about
+    /// which inputs they accept.  But first, we should verify that
+    /// `base32`'s behavior is actually what we want.
+    #[test]
+    fn decode_arbitrary_padded(string in string_regex("[a-z0-9]{0,32}={0,8}").unwrap()) {
+        let actual = Base32Ct::decode_vec(&string);
+        let expected = base32::decode(RFC4648_PADDED, &string);
+        // assert_eq!(actual.ok(), expected);
+        if let (Ok(a), Some(b)) = (actual, expected) {
+            assert_eq!(a, b);
+        }
+    }
+
+    /// Make sure that, if base32ct and base32 _both_ decode a value
+    /// when expecting unpadded inputs, they give the same output.
+    ///
+    /// TODO: See note above.
+    #[test]
+    fn decode_arbitrary_unpadded(string in string_regex("[a-z0-9]{0,32}={0,8}").unwrap()) {
+        let actual = Base32UnpaddedCt::decode_vec(&string);
+        let expected = base32::decode(RFC4648_UNPADDED, &string);
+        // assert_eq!(actual.ok(), expected);
+        if let (Ok(a), Some(b)) = (actual, expected) {
+            assert_eq!(a, b);
+        }
+    }
 }
diff --git a/base64ct/tests/proptests.rs b/base64ct/tests/proptests.rs
index c60cf16d7..6881bcd3b 100644
--- a/base64ct/tests/proptests.rs
+++ b/base64ct/tests/proptests.rs
@@ -5,7 +5,7 @@
 // warning: use of deprecated function `base64::encode`: Use Engine::encode
 #![allow(deprecated)]
 
-use base64ct::{Base64 as Base64ct, Encoding};
+use base64ct::{Base64 as Base64ct, Base64Unpadded as Base64UnpaddedCt, Encoding};
 use proptest::{prelude::*, string::*};
 
 /// Incremental Base64 decoder.
@@ -148,4 +148,23 @@ proptest! {
 
         prop_assert_eq!(expected, encoder.finish().unwrap());
     }
+
+    /// Make sure that base64ct and base64 both decode the same values
+    /// when expecting padded inputs, and produce the same outputs for those values.
+    #[test]
+    fn decode_arbitrary_padded(string in string_regex("[a-zA-Z0-9/+=?]{0,256}").unwrap()) {
+        let actual = Base64ct::decode_vec(&string);
+        let expected = base64::decode( &string);
+        assert_eq!(actual.ok(), expected.ok());
+    }
+
+    /// Make sure that base64ct and base64 both decode the same values
+    /// when expecting unpadded inputs, and produce the same outputs for those values.
+    #[test]
+    fn decode_arbitrary_unpadded(string in string_regex("[a-zA-Z0-9/+=?]{0,256}").unwrap()) {
+        use base64::{engine::general_purpose::STANDARD_NO_PAD, Engine as _};
+        let actual = Base64UnpaddedCt::decode_vec(&string);
+        let expected = STANDARD_NO_PAD.decode(&string);
+        assert_eq!(actual.ok(), expected.ok());
+    }
 }