diff --git a/configure.ac b/configure.ac
index 37b80a4..496db1d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -12,11 +12,11 @@ AS_CASE([$host_os],
   [freebsd*], [PLATFORM="freebsd"],
   [PLATFORM="nix"])
 
-PKG_CHECK_MODULES([openssl], [openssl], [PC_REQUIRES+=(openssl)],
+PKG_CHECK_MODULES([openssl], [openssl], [PC_REQUIRES="openssl ${PC_REQUIRES}"],
             [AC_CHECK_HEADER([openssl/ssl.h],
                              [
                               openssl_LIBS="-lssl -lcrypto"
-                              PC_LIBS+=($openssl_LIBS)
+                              PC_LIBS="${openssl_LIBS} ${PC_LIBS}"
                              ],
                              [AC_MSG_ERROR([openssl not found; openssl required])]
                             )])
@@ -31,7 +31,7 @@ if test "x$with_libxml2" != xno; then
   PKG_CHECK_MODULES([libxml2], [libxml-2.0 >= 2.7],
                     [
                      with_libxml2=yes
-                     PC_REQUIRES+=(libxml-2.0)
+                     PC_REQUIRES="libxml-2.0 ${PC_REQUIRES}"
                     ],
                     [
                      old_CFLAGS=$CFLAGS
@@ -41,19 +41,19 @@ if test "x$with_libxml2" != xno; then
                                       with_libxml2=yes
                                       libxml2_CFLAGS="-I${includedir}/libxml2"
                                       libxml2_LIBS="-lxml2"
-                                      PC_LIBS+=($libxml2_LIBS)
-                                      PC_CFLAGS+=($libxml2_CFLAGS)
+                                      PC_LIBS="${libxml2_LIBS} ${PC_LIBS}"
+                                      PC_CFLAGS="${libxml2_CFLAGS} ${PC_CFLAGS}"
                                      ],
                                      [AC_MSG_ERROR([libxml2 not found.])])
                      CFLAGS=$old_CFLAGS
                     ])
 else
   PKG_CHECK_MODULES([expat], [expat >= 2.0.0],
-                    [PC_REQUIRES+=(expat)],
+                    [PC_REQUIRES="expat ${PC_REQUIRES} "],
                     [AC_CHECK_HEADER([expat.h],
                                      [
                                       expat_LIBS="-lexpat"
-                                      PC_LIBS+=($expat_LIBS)
+                                      PC_LIBS="${expat_LIBS} ${PC_LIBS}"
                                      ],
                                      [AC_MSG_ERROR([expat not found; expat required.])]
                                     )
@@ -79,7 +79,7 @@ if test "x$PLATFORM" != xfreebsd; then
         AC_CHECK_LIB([resolv], [res_query], [],
             [AC_CHECK_LIB([resolv], [__res_query], [],
                 [AC_MSG_ERROR([libresolv not found; libresolv required.])])])
-        PC_LIBS+=(-lresolv)
+        PC_LIBS="-lresolv ${PC_LIBS}"
 else
         AC_MSG_NOTICE([skipping libresolv checks for freebsd])
 fi
@@ -96,9 +96,9 @@ m4_ifdef([PKG_INSTALLDIR], [PKG_INSTALLDIR],
 
 AM_CONDITIONAL([PARSER_EXPAT], [test x$with_parser != xlibxml2])
 
-AC_SUBST([PC_REQUIRES], [${PC_REQUIRES[[@]]}])
-AC_SUBST([PC_CFLAGS], [${PC_CFLAGS[[@]]}])
-AC_SUBST([PC_LIBS], [${PC_LIBS[[@]]}])
+AC_SUBST([PC_REQUIRES], [${PC_REQUIRES}])
+AC_SUBST([PC_CFLAGS], [${PC_CFLAGS}])
+AC_SUBST([PC_LIBS], [${PC_LIBS}])
 
 AC_SUBST(PARSER_NAME)
 AC_SUBST(PARSER_CFLAGS)