diff --git a/lib/entry/libimagentrytag/src/tag.rs b/lib/entry/libimagentrytag/src/tag.rs
index 58573cef..3cba2016 100644
--- a/lib/entry/libimagentrytag/src/tag.rs
+++ b/lib/entry/libimagentrytag/src/tag.rs
@@ -29,15 +29,15 @@ pub fn is_tag(s: String) -> Result<(), String> {
     is_tag_str(&s).map_err(|_| format!("The string '{}' is not a valid tag", s))
 }
 
-pub fn is_tag_str(s: &String) -> Result<(), Error> {
+pub fn is_tag_str(s: &str) -> Result<(), Error> {
     use filters::filter::Filter;
     trace!("Checking whether '{}' is a valid tag", s);
 
-    let is_lower      = |s: &String| s.chars().all(|c| c.is_lowercase());
-    let no_whitespace = |s: &String| s.chars().all(|c| !c.is_whitespace());
-    let is_alphanum   = |s: &String| s.chars().all(|c| c.is_alphanumeric());
+    let is_lower      = |s: &&str| s.chars().all(|c| c.is_lowercase());
+    let no_whitespace = |s: &&str| s.chars().all(|c| !c.is_whitespace());
+    let is_alphanum   = |s: &&str| s.chars().all(|c| c.is_alphanumeric());
 
-    if is_lower.and(no_whitespace).and(is_alphanum).filter(s) {
+    if is_lower.and(no_whitespace).and(is_alphanum).filter(&s) {
         Ok(())
     } else {
         Err(format_err!("The string '{}' is not a valid tag", s))
diff --git a/lib/entry/libimagentrytag/src/tagable.rs b/lib/entry/libimagentrytag/src/tagable.rs
index 51dd7c04..f6d8d6b1 100644
--- a/lib/entry/libimagentrytag/src/tagable.rs
+++ b/lib/entry/libimagentrytag/src/tagable.rs
@@ -62,7 +62,7 @@ impl Tagable for Entry {
             .map(|header| {
                 header.values
                     .iter()
-                    .map(is_tag_str)
+                    .map(|val| is_tag_str(val))
                     .collect::<Result<_>>()?;
 
                 Ok(header.values)
@@ -73,7 +73,7 @@ impl Tagable for Entry {
     fn set_tags(&mut self, ts: &[Tag]) -> Result<()> {
         let _ = ts
             .iter()
-            .map(is_tag_str)
+            .map(|val| is_tag_str(val))
             .collect::<Result<Vec<_>>>()?;
 
         let header = TagHeader {