diff --git a/configure.in b/configure.in
index ac125ee044e0..6a9e0b5e275d 100644
--- a/configure.in
+++ b/configure.in
@@ -1915,13 +1915,13 @@ case "$host" in
 esac
 
 dnl We require version 2.5 or newer of Python to build.
-AC_MSG_CHECKING([for minimum required Python version >= $PYTHON_VERSION])
+AC_MSG_CHECKING([for Python version >= $PYTHON_VERSION but not 3.x])
 changequote(,)
-$PYTHON -c "import sys; sys.exit(sys.version[:3] < sys.argv[1])" $PYTHON_VERSION
+$PYTHON -c "import sys; sys.exit(sys.version[:3] < sys.argv[1] or sys.version[:2] != '2.')" $PYTHON_VERSION
 _python_res=$?
 changequote([,])
 if test "$_python_res" != 0; then
-    AC_MSG_ERROR([Python $PYTHON_VERSION or higher is required.])
+    AC_MSG_ERROR([Python $PYTHON_VERSION or higher (but not Python 3.x) is required.])
 fi
 AC_MSG_RESULT([yes])
 
diff --git a/js/src/configure.in b/js/src/configure.in
index a5963dc4c1c0..a3d3eb9f2e76 100644
--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -990,7 +990,7 @@ else
     AC_MSG_RESULT([yes])    
 fi
 
-MOZ_PATH_PROGS(PYTHON, $PYTHON python2.6 python2.5 python2.4 python)
+MOZ_PATH_PROGS(PYTHON, $PYTHON python2.7 python2.6 python2.5 python)
 if test -z "$PYTHON"; then
     AC_MSG_ERROR([python was not found in \$PATH])
 fi
@@ -1904,13 +1904,13 @@ esac
 
 dnl We require version 2.4 or newer of Python to build,
 dnl and 2.5 or newer on Windows.
-AC_MSG_CHECKING([for minimum required Python version >= $PYTHON_VERSION])
+AC_MSG_CHECKING([for Python version >= $PYTHON_VERSION but not 3.x])
 changequote(,)
-$PYTHON -c "import sys; sys.exit(sys.version[:3] < sys.argv[1])" $PYTHON_VERSION
+$PYTHON -c "import sys; sys.exit(sys.version[:3] < sys.argv[1] or sys.version[:2] != '2.')" $PYTHON_VERSION
 _python_res=$?
 changequote([,])
 if test "$_python_res" != 0; then
-    AC_MSG_ERROR([Python $PYTHON_VERSION or higher is required.])
+    AC_MSG_ERROR([Python $PYTHON_VERSION or higher (but not Python 3.x) is required.])
 fi
 AC_MSG_RESULT([yes])