diff --git a/hex-literal/CHANGELOG.md b/hex-literal/CHANGELOG.md
index 43edcac4..46e77e34 100644
--- a/hex-literal/CHANGELOG.md
+++ b/hex-literal/CHANGELOG.md
@@ -12,6 +12,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - More tests for `hex!()` macro
 - More internal documentation
 
+### Fixed
+- Make `hex!()` error when forward slash encountered as last byte
+
 ## 0.3.3 (2021-07-17)
 ### Added
 - Accept sequence of string literals ([#519])
diff --git a/hex-literal/src/comments.rs b/hex-literal/src/comments.rs
index 02dd6993..135e6d53 100644
--- a/hex-literal/src/comments.rs
+++ b/hex-literal/src/comments.rs
@@ -28,6 +28,8 @@ impl<I: Iterator<Item = u8>> Iterator for ExcludingComments<I> {
                 State::BlockComment | State::PotentiallyLeavingBlockComment => {
                     panic!("block comment not terminated with */")
                 }
+                // No more bytes after a single '/'
+                State::PotentialComment { .. } => panic!("encountered invalid character: `/`"),
                 _ => {}
             }
         }