diff --git a/configure.ac b/configure.ac
index 29edcb6a..f456bd21 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1109,43 +1109,44 @@ elif test "x${force_tls}" = "x1" ; then
 fi
 
 dnl ============================================================================
-dnl Check for ffsl(3), then __builtin_ffsl(), and fail if neither are found.
+dnl Check for  __builtin_ffsl(), then ffsl(3), and fail if neither are found.
 dnl One of those two functions should (theoretically) exist on all platforms
 dnl that jemalloc currently has a chance of functioning on without modification.
 dnl We additionally assume ffs() or __builtin_ffs() are defined if
 dnl ffsl() or __builtin_ffsl() are defined, respectively.
-JE_COMPILABLE([a program using ffsl], [
+JE_COMPILABLE([a program using __builtin_ffsl], [
 #include <stdio.h>
 #include <strings.h>
 #include <string.h>
 ], [
 	{
-		int rv = ffsl(0x08);
+		int rv = __builtin_ffsl(0x08);
 		printf("%d\n", rv);
 	}
-], [je_cv_function_ffsl])
-if test "x${je_cv_function_ffsl}" == "xyes" ; then
-  AC_DEFINE([JEMALLOC_INTERNAL_FFSL], [ffsl])
-  AC_DEFINE([JEMALLOC_INTERNAL_FFS], [ffs])
+], [je_cv_gcc_builtin_ffsl])
+if test "x${je_cv_gcc_builtin_ffsl}" == "xyes" ; then
+  AC_DEFINE([JEMALLOC_INTERNAL_FFSL], [__builtin_ffsl])
+  AC_DEFINE([JEMALLOC_INTERNAL_FFS], [__builtin_ffs])
 else
-  JE_COMPILABLE([a program using __builtin_ffsl], [
+  JE_COMPILABLE([a program using ffsl], [
   #include <stdio.h>
   #include <strings.h>
   #include <string.h>
   ], [
 	{
-		int rv = __builtin_ffsl(0x08);
+		int rv = ffsl(0x08);
 		printf("%d\n", rv);
 	}
-  ], [je_cv_gcc_builtin_ffsl])
-  if test "x${je_cv_gcc_builtin_ffsl}" == "xyes" ; then
-    AC_DEFINE([JEMALLOC_INTERNAL_FFSL], [__builtin_ffsl])
-    AC_DEFINE([JEMALLOC_INTERNAL_FFS], [__builtin_ffs])
+  ], [je_cv_function_ffsl])
+  if test "x${je_cv_function_ffsl}" == "xyes" ; then
+    AC_DEFINE([JEMALLOC_INTERNAL_FFSL], [ffsl])
+    AC_DEFINE([JEMALLOC_INTERNAL_FFS], [ffs])
   else
     AC_MSG_ERROR([Cannot build without ffsl(3) or __builtin_ffsl()])
   fi
 fi
 
+
 dnl ============================================================================
 dnl Check for atomic(9) operations as provided on FreeBSD.