diff --git a/build.sh b/build.sh
index a9565bc..d8485f0 100755
--- a/build.sh
+++ b/build.sh
@@ -29,7 +29,9 @@ esac; shift; done;
 [ -f ../midipix_build.vars ] && . ../midipix_build.vars;
 . ./build.vars;
 clear_env_with_except ${CLEAR_ENV_VARS_EXCEPT};
-check_path_vars ${CHECK_PATH_VARS}; check_prereqs ${CHECK_PREREQ_CMDS};
+check_path_vars ${CHECK_PATH_VARS};
+check_prereq_cmds ${CHECK_PREREQ_CMDS};
+check_prereq_files ${CHECK_PREREQ_FILES};
 if ! [ -d ${PREFIX} ]; then
 	mkdir ${PREFIX};
 fi;
diff --git a/build.subr b/build.subr
index 6122212..7858378 100644
--- a/build.subr
+++ b/build.subr
@@ -214,15 +214,27 @@ check_path_vars() {
 };
 
 # Check whether all supplied command names resolve.
-check_prereqs() {
+check_prereq_cmds() {
 	while [ ${#} -gt 0 ]; do
 		if ! command -v ${1} >/dev/null; then
-			_cp_missing_list="${1}${_cp_missing_list:+ ${_cp_missing_list}}";
+			_cpc_missing_list="${1}${_cpc_missing_list:+ ${_cpc_missing_list}}";
 		fi; shift;
 	done;
-	if [ -n "${_cp_missing_list}" ]; then
-		log_msg failexit "Error: missing prerequisite command(s): ${_cp_missing_list}.";
-	fi; unset _cp_missing_list;
+	if [ -n "${_cpc_missing_list}" ]; then
+		log_msg failexit "Error: missing prerequisite command(s): ${_cpc_missing_list}.";
+	fi; unset _cpc_missing_list;
+};
+
+# Check whether all supplied pathnames resolve.
+check_prereq_files() {
+	while [ ${#} -gt 0 ]; do
+		if [ ! -e ${1} ]; then
+			_cpf_missing_list="${1}${_cpf_missing_list:+ ${_cpf_missing_list}}";
+		fi; shift;
+	done;
+	if [ -n "${_cpf_missing_list}" ]; then
+		log_msg failexit "Error: missing prerequisite file(s): ${_cpf_missing_list}.";
+	fi; unset _cpf_missing_list;
 };
 
 # Clear the environment by unsetting each exported variable except
diff --git a/build.vars b/build.vars
index ccb7b05..e6dd5a3 100644
--- a/build.vars
+++ b/build.vars
@@ -15,6 +15,7 @@
 : ${BUILD_STATUS_IN_PROGRESS_FNAME:=${PREFIX}/BUILD_IN_PROGRESS};
 : ${CFLAGS_DEFAULT:=-g3 -O0};
 : ${CHECK_PREREQ_CMDS:="aclocal autoconf autopoint bunzip2 flex git gunzip install libtool make makeinfo mktemp openssl patch sed sort tar tee tr sha256sum wget xz"};
+: ${CHECK_PREREQ_FILES:="/usr/include/gmpxx.h /usr/include/mpc.h /usr/include/mpfr.h"};
 : ${CHECK_PATH_VARS:="PREFIX PREFIX_NATIVE WORKDIR"};
 : ${CLEAR_ENV_VARS_EXCEPT:="HOME PATH SHELL TERM USER"};
 : ${GITROOT:=git://midipix.org};