diff --git a/NEWS b/NEWS
index fdad83c..1af3def 100644
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,10 @@ GNU grep NEWS                                    -*- outline -*-
 
 * Noteworthy changes in release ?.? (????-??-??) [?]
 
+** Improvements
+
+  Performance has improved for very long strings in patterns.
+
 
 * Noteworthy changes in release 2.20 (2014-06-03) [stable]
 
diff --git a/bootstrap.conf b/bootstrap.conf
index 9f3457d..1ab730d 100644
--- a/bootstrap.conf
+++ b/bootstrap.conf
@@ -77,6 +77,7 @@ stdlib
 stpcpy
 strerror
 string
+strstr
 strtoull
 strtoumax
 sys_stat
diff --git a/src/dfa.c b/src/dfa.c
index 48a83cd..522a027 100644
--- a/src/dfa.c
+++ b/src/dfa.c
@@ -3752,19 +3752,6 @@ icatalloc (char *old, char const *new)
   return result;
 }
 
-static char *_GL_ATTRIBUTE_PURE
-istrstr (char const *lookin, char const *lookfor)
-{
-  char const *cp;
-  size_t len;
-
-  len = strlen (lookfor);
-  for (cp = lookin; *cp != '\0'; ++cp)
-    if (strncmp (cp, lookfor, len) == 0)
-      return (char *) cp;
-  return NULL;
-}
-
 static void
 freelist (char **cpp)
 {
@@ -3780,7 +3767,7 @@ enlist (char **cpp, char *new, size_t len)
   new[len] = '\0';
   /* Is there already something in the list that's new (or longer)?  */
   for (i = 0; cpp[i] != NULL; ++i)
-    if (istrstr (cpp[i], new) != NULL)
+    if (strstr (cpp[i], new) != NULL)
       {
         free (new);
         return cpp;
@@ -3788,7 +3775,7 @@ enlist (char **cpp, char *new, size_t len)
   /* Eliminate any obsoleted strings.  */
   j = 0;
   while (cpp[j] != NULL)
-    if (istrstr (new, cpp[j]) == NULL)
+    if (strstr (new, cpp[j]) == NULL)
       ++j;
     else
       {