diff --git a/src/mod/endpoints/mod_opal/Makefile.am b/src/mod/endpoints/mod_opal/Makefile.am
index bface20beb..e28129d9ba 100644
--- a/src/mod/endpoints/mod_opal/Makefile.am
+++ b/src/mod/endpoints/mod_opal/Makefile.am
@@ -6,6 +6,6 @@ PKG_DIR=/usr/local/lib/pkgconfig
 #DEBUG_SUFFIX:=--define-variable=suffix=_d
 mod_LTLIBRARIES = mod_opal.la
 mod_opal_la_SOURCES  = mod_opal.cpp
-mod_opal_la_CFLAGS   = $(AM_CFLAGS) `PKG_CONFIG_PATH=$(PKG_CONFIG_PATH):$(PKG_DIR) pkg-config opal $(DEBUG_SUFFIX) --cflags`
+mod_opal_la_CFLAGS   = $(AM_CFLAGS) $(shell PKG_CONFIG_PATH=$(PKG_CONFIG_PATH):$(PKG_DIR) pkg-config opal $(DEBUG_SUFFIX) --cflags)
 mod_opal_la_LIBADD   = $(switch_builddir)/libfreeswitch.la
-mod_opal_la_LDFLAGS  = -avoid-version -module -no-undefined -shared `pkg-config opal $(DEBUG_SUFFIX) --libs`
+mod_opal_la_LDFLAGS  = -avoid-version -module -no-undefined -shared $(shell pkg-config opal $(DEBUG_SUFFIX) --libs)