--- a/lib/setenv.c
+++ b/lib/setenv.c
@@ -49,7 +49,7 @@
 #endif
 
 #if _LIBC
-/* This lock protects against simultaneous modifications of `environ'.  */
+/* This lock protects against simultaneous modifications of 'environ'.  */
 # include <bits/libc-lock.h>
 __libc_lock_define_initialized (static, envlock)
 # define LOCK   __libc_lock_lock (envlock)
@@ -103,11 +103,11 @@
 static char **last_environ;
 
 
-/* This function is used by `setenv' and `putenv'.  The difference between
+/* This function is used by 'setenv' and 'putenv'.  The difference between
    the two functions is that for the former must create a new string which
-   is then placed in the environment, while the argument of `putenv'
+   is then placed in the environment, while the argument of 'putenv'
    must be used directly.  This is all complicated by the fact that we try
-   to reuse values once generated for a `setenv' call since we can never
+   to reuse values once generated for a 'setenv' call since we can never
    free the strings.  */
 int
 __add_to_environ (const char *name, const char *value, const char *combined,
@@ -299,7 +299,7 @@
   return __add_to_environ (name, value, NULL, replace);
 }
 
-/* The `clearenv' was planned to be added to POSIX.1 but probably
+/* The 'clearenv' was planned to be added to POSIX.1 but probably
    never made it.  Nevertheless the POSIX.9 standard (POSIX bindings
    for Fortran 77) requires this function.  */
 int