diff --git a/configure.ac b/configure.ac
index 5b363fb..cf8fdc5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1718,11 +1718,21 @@ GMP_H_ANSI
 
 
 # The C compiler on the build system, and associated tests.
+if test "$cross_compiling" == "no" ; then
+# native build, native tools
 GMP_PROG_CC_FOR_BUILD
 GMP_PROG_CPP_FOR_BUILD
 GMP_PROG_EXEEXT_FOR_BUILD
 GMP_C_FOR_BUILD_ANSI
 GMP_CHECK_LIBM_FOR_BUILD
+else
+# cross build, <TOOL>_FOR_BUILD disabled by vcpkg
+AC_SUBST(CC_FOR_BUILD,"false")
+AC_SUBST(CPP_FOR_BUILD,"false")
+AC_SUBST(EXEEXT_FOR_BUILD,"")
+AC_SUBST(U_FOR_BUILD,"")
+AC_SUBST(LIBM_FOR_BUILD,"")
+fi
 
 # How to assemble, used with CFLAGS etc, see mpn/Makeasm.am.
 # Using the compiler is a lot easier than figuring out how to invoke the