diff --git a/Misc/NEWS b/Misc/NEWS
index c57b165..58675e8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -316,6 +316,9 @@
 Build
 -----
 
+- Cross compiling needs host and build settings. configure no longer
+  creates a broken PYTHON_FOR_BUILD variable when --build is missing.
+
 - Fix cross compiling issue in setup.py, ensure that lib_dirs and inc_dirs are
   defined in cross compiling mode, too.
 
diff --git a/configure b/configure
index 5fc460f..6407cc4 100755
--- a/configure
+++ b/configure
@@ -2943,6 +2943,8 @@
 $as_echo "$interp" >&6; }
 	PYTHON_FOR_BUILD="_PYTHON_PROJECT_BASE=$srcdir"' _PYTHON_HOST_PLATFORM=$(_PYTHON_HOST_PLATFORM) PYTHONPATH=$(srcdir)/Lib:$(srcdir)/Lib/plat-$(MACHDEP) '$interp
     fi
+elif test "$cross_compiling" = maybe; then
+    as_fn_error $? "Cross compiling required --host=HOST-TUPLE and --build=ARCH" "$LINENO" 5
 else
     PYTHON_FOR_BUILD='./$(BUILDPYTHON) -E'
 fi
diff --git a/configure.ac b/configure.ac
index 2738703..ef58a9f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -67,6 +67,8 @@
         AC_MSG_RESULT($interp)
 	PYTHON_FOR_BUILD="_PYTHON_PROJECT_BASE=$srcdir"' _PYTHON_HOST_PLATFORM=$(_PYTHON_HOST_PLATFORM) PYTHONPATH=$(srcdir)/Lib:$(srcdir)/Lib/plat-$(MACHDEP) '$interp
     fi
+elif test "$cross_compiling" = maybe; then
+    AC_MSG_ERROR([Cross compiling required --host=HOST-TUPLE and --build=ARCH])
 else
     PYTHON_FOR_BUILD='./$(BUILDPYTHON) -E'
 fi