diff --git a/clippy_lints/src/booleans.rs b/clippy_lints/src/booleans.rs
index c5da0af6f4d1..9e19edcca115 100644
--- a/clippy_lints/src/booleans.rs
+++ b/clippy_lints/src/booleans.rs
@@ -10,6 +10,7 @@ use rustc::{declare_lint_pass, declare_tool_lint};
 use rustc_errors::Applicability;
 use syntax::ast::LitKind;
 use syntax::source_map::Span;
+use syntax_pos::symbol::Symbol;
 
 declare_clippy_lint! {
     /// **What it does:** Checks for boolean expressions that can be written more
@@ -255,7 +256,7 @@ fn simplify_not(cx: &LateContext<'_, '_>, expr: &Expr) -> Option<String> {
                 .iter()
                 .cloned()
                 .flat_map(|(a, b)| vec![(a, b), (b, a)])
-                .find(|&(a, _)| a == path.ident.name.as_str())
+                .find(|&(a, _)| Symbol::intern(a) == path.ident.name)
                 .and_then(|(_, neg_method)| Some(format!("{}.{}()", snippet_opt(cx, args[0].span)?, neg_method)))
         },
         _ => None,
diff --git a/clippy_lints/src/functions.rs b/clippy_lints/src/functions.rs
index 5b2619aa9ba7..43b2372e342c 100644
--- a/clippy_lints/src/functions.rs
+++ b/clippy_lints/src/functions.rs
@@ -12,6 +12,7 @@ use rustc_errors::Applicability;
 use rustc_target::spec::abi::Abi;
 use syntax::ast::Attribute;
 use syntax::source_map::Span;
+use syntax_pos::symbol::Symbol;
 
 declare_clippy_lint! {
     /// **What it does:** Checks for functions with too many parameters.
@@ -464,7 +465,7 @@ fn check_must_use_candidate<'a, 'tcx>(
 fn must_use_attr(attrs: &[Attribute]) -> Option<&Attribute> {
     attrs
         .iter()
-        .find(|attr| attr.ident().map_or(false, |ident| "must_use" == &ident.as_str()))
+        .find(|attr| attr.ident().map_or(false, |ident| Symbol::intern("must_use") == ident.name))
 }
 
 fn returns_unit(decl: &hir::FnDecl) -> bool {