diff --git a/src/common/if_match.rs b/src/common/if_match.rs
index bc2a8479..267bd760 100644
--- a/src/common/if_match.rs
+++ b/src/common/if_match.rs
@@ -108,4 +108,38 @@ mod tests {
 
         assert!(if_match.precondition_passes(&foo));
     }
+
+    #[test]
+    fn decode_empty() {
+        use crate::Header;
+
+        assert!(IfMatch::decode(&mut [].iter()).is_err());
+        assert!(IfMatch::decode(&mut [HeaderValue::from_static("")].iter()).is_err());
+        assert!(IfMatch::decode(&mut [HeaderValue::from_static("   ")].iter()).is_err());
+    }
+
+    #[test]
+    fn decode_invalid() {
+        use crate::Header;
+
+        assert!(IfMatch::decode(&mut [HeaderValue::from_static("no-quotes")].iter()).is_err());
+        assert!(IfMatch::decode(&mut [HeaderValue::from_static("\"foo\", bad")].iter()).is_err());
+    }
+
+    #[test]
+    fn decode_valid() {
+        use crate::Header;
+
+        let any = IfMatch::decode(&mut [HeaderValue::from_static("*")].iter()).unwrap();
+        assert!(any.is_any());
+
+        let any_spaced = IfMatch::decode(&mut [HeaderValue::from_static(" * ")].iter()).unwrap();
+        assert!(any_spaced.is_any());
+
+        let tags =
+            IfMatch::decode(&mut [HeaderValue::from_static("\"foo\", \"bar\"")].iter()).unwrap();
+        assert!(tags.precondition_passes(&ETag::from_static("\"foo\"")));
+        assert!(tags.precondition_passes(&ETag::from_static("\"bar\"")));
+        assert!(!tags.precondition_passes(&ETag::from_static("\"baz\"")));
+    }
 }
diff --git a/src/common/if_none_match.rs b/src/common/if_none_match.rs
index 89a80dc0..d259faee 100644
--- a/src/common/if_none_match.rs
+++ b/src/common/if_none_match.rs
@@ -108,4 +108,41 @@ mod tests {
 
         assert!(!if_none.precondition_passes(&foo));
     }
+
+    #[test]
+    fn decode_empty() {
+        use crate::Header;
+
+        assert!(IfNoneMatch::decode(&mut [].iter()).is_err());
+        assert!(IfNoneMatch::decode(&mut [HeaderValue::from_static("")].iter()).is_err());
+        assert!(IfNoneMatch::decode(&mut [HeaderValue::from_static("   ")].iter()).is_err());
+    }
+
+    #[test]
+    fn decode_invalid() {
+        use crate::Header;
+
+        assert!(IfNoneMatch::decode(&mut [HeaderValue::from_static("no-quotes")].iter()).is_err());
+        assert!(
+            IfNoneMatch::decode(&mut [HeaderValue::from_static("\"foo\", bad")].iter()).is_err()
+        );
+    }
+
+    #[test]
+    fn decode_valid() {
+        use crate::Header;
+
+        let any = IfNoneMatch::decode(&mut [HeaderValue::from_static("*")].iter()).unwrap();
+        assert!(!any.precondition_passes(&ETag::from_static("\"foo\"")));
+
+        let any_spaced =
+            IfNoneMatch::decode(&mut [HeaderValue::from_static(" * ")].iter()).unwrap();
+        assert!(!any_spaced.precondition_passes(&ETag::from_static("\"foo\"")));
+
+        let tags = IfNoneMatch::decode(&mut [HeaderValue::from_static("\"foo\", \"bar\"")].iter())
+            .unwrap();
+        assert!(!tags.precondition_passes(&ETag::from_static("\"foo\"")));
+        assert!(!tags.precondition_passes(&ETag::from_static("\"bar\"")));
+        assert!(tags.precondition_passes(&ETag::from_static("\"baz\"")));
+    }
 }
diff --git a/src/util/entity.rs b/src/util/entity.rs
index 554bffb2..ff2942bd 100644
--- a/src/util/entity.rs
+++ b/src/util/entity.rs
@@ -252,10 +252,29 @@ impl super::TryFromValues for EntityTagRange {
     where
         I: Iterator<Item = &'i HeaderValue>,
     {
-        let flat = FlatCsv::try_from_values(values)?;
-        if flat.value == "*" {
+        let mut values = values.peekable();
+        if values.peek().is_none() {
+            return Err(Error::invalid());
+        }
+        let flat = FlatCsv::try_from_values(&mut values)?;
+        if flat
+            .value
+            .to_str()
+            .map(|s| s.trim() == "*")
+            .unwrap_or(false)
+        {
             Ok(EntityTagRange::Any)
         } else {
+            let mut count = 0;
+            for s in flat.iter() {
+                if EntityTag::<&str>::parse(s).is_none() {
+                    return Err(Error::invalid());
+                }
+                count += 1;
+            }
+            if count == 0 {
+                return Err(Error::invalid());
+            }
             Ok(EntityTagRange::Tags(flat))
         }
     }