diff --git a/js/src/configure.in b/js/src/configure.in
index a3400b6d7a62..14c6b30c8275 100644
--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -3115,9 +3115,10 @@ dnl Checks for library functions.
 dnl ========================================================
 AC_PROG_GCC_TRADITIONAL
 AC_FUNC_MEMCMP
-AC_CHECK_FUNCS([fchmod flockfile getpagesize lchown localtime_r lstat64 \
-                memmove random rint sbrk snprintf stat64 statvfs statvfs64 \
-                strerror strtok_r truncate64])
+
+AC_CHECK_FUNCS([fchmod flockfile getc_unlocked _getc_nolock getpagesize \
+                lchown localtime_r lstat64 memmove random rint sbrk snprintf \
+                stat64 statvfs statvfs64 strerror strtok_r truncate64])
 
 dnl Windows functions, for mingw.
 AC_TRY_LINK([#include <windows.h>],
diff --git a/js/src/jsscan.cpp b/js/src/jsscan.cpp
index 46f588795ef2..7cbd7ef3839f 100644
--- a/js/src/jsscan.cpp
+++ b/js/src/jsscan.cpp
@@ -226,12 +226,13 @@ JSTokenStream::close(JSContext *cx)
         cx->free((void *) filename);
 }
 
-#ifdef XP_WIN
-#ifdef WINCE
-#define getc_unlocked getc
+/* Use the fastest available getc. */
+#if defined(HAVE_GETC_UNLOCKED)
+#define fast_getc getc_unlocked
+#elif defined(HAVE__GETC_NOLOCK)
+#define fast_getc _getc_nolock
 #else
-#define getc_unlocked _getc_nolock
-#endif
+#define fast_getc getc
 #endif
 
 JS_FRIEND_API(int)
@@ -245,7 +246,7 @@ js_fgets(char *buf, int size, FILE *file)
         return -1;
 
     crflag = JS_FALSE;
-    for (i = 0; i < n && (c = getc_unlocked(file)) != EOF; i++) {
+    for (i = 0; i < n && (c = fast_getc(file)) != EOF; i++) {
         buf[i] = c;
         if (c == '\n') {        /* any \n ends a line */
             i++;                /* keep the \n; we know there is room for \0 */