diff --git a/metapkg/packages/base.py b/metapkg/packages/base.py
index c73b19f..bf56ff2 100644
--- a/metapkg/packages/base.py
+++ b/metapkg/packages/base.py
@@ -1023,13 +1023,34 @@ def configure_dependency(
             root = build.get_install_dir(pkg, relative_to="pkgbuild")
             path = root / build.get_full_install_prefix().relative_to("/")
             rel_path = f'$(pwd)/"{path}"'
-            configure_flags[f"{var_prefix}_CFLAGS"] = f"!-I{rel_path}/include/"
+
             dep_ldflags = build.sh_get_bundled_shlib_ldflags(
-                pkg, relative_to="pkgbuild"
-            )
-            configure_flags[f"{var_prefix}_LIBS"] = f"!{dep_ldflags}"
+                pkg, relative_to="pkgbuild")
+
+            if var_prefix:
+                build.sh_append_flags(
+                    configure_flags,
+                    f"{var_prefix}_CFLAGS",
+                    f"-I{rel_path}/include/",
+                )
+                build.sh_append_flags(
+                    configure_flags,
+                    f"{var_prefix}_LIBS",
+                    dep_ldflags,
+                )
+            else:
+                build.sh_append_flags(
+                    configure_flags,
+                    "CFLAGS",
+                    f"-I{rel_path}/include/",
+                )
+                build.sh_append_flags(
+                    configure_flags,
+                    f"LDFLAGS",
+                    dep_ldflags,
+                )
 
-            ldflags = f"!-L{rel_path}/lib/"
+            ldflags = f"-L{rel_path}/lib/"
 
             if platform.system() == "Darwin":
                 # In case ./configure tries to compile and test a program
@@ -1039,7 +1060,7 @@ def configure_dependency(
             else:
                 ldflags += f'" "-Wl,-rpath-link,{rel_path}/lib'
 
-            configure_flags["LDFLAGS"] = ldflags
+            build.sh_append_flags(configure_flags, f"LDFLAGS", ldflags)
 
         elif build.is_stdlib(pkg):
             configure_flags[