diff -up pkg-config-0.28/pkg.c.envvar pkg-config-0.28/pkg.c
--- pkg-config-0.28/pkg.c.envvar	2013-01-22 14:11:59.000000000 +0100
+++ pkg-config-0.28/pkg.c	2015-06-09 21:19:51.648018495 +0200
@@ -1012,6 +1012,24 @@ define_global_variable (const char *varn
 }
 
 char *
+var_to_env_var (const char *pkg, const char *var)
+{
+  char *new = g_strconcat ("PKG_CONFIG_", pkg, "_", var, NULL);
+  char *p;
+  for (p = new; *p != 0; p++)
+    {
+      char c = g_ascii_toupper (*p);
+
+      if (!g_ascii_isalnum (c))
+        c = '_';
+
+      *p = c;
+    }
+
+  return new;
+}
+
+char *
 package_get_var (Package *pkg,
                  const char *var)
 {
@@ -1019,7 +1037,20 @@ package_get_var (Package *pkg,
 
   if (globals)
     varval = g_strdup (g_hash_table_lookup (globals, var));
-  
+
+  if (pkg->key)
+    {
+      char *env_var = var_to_env_var (pkg->key, var);
+      const char *env_var_content = g_getenv (env_var);
+      g_free (env_var);
+      if (env_var_content)
+        {
+          debug_spew ("Overriding variable '%s' from environment\n", var);
+          return g_strdup (env_var_content);
+        }
+    }
+
+
   if (varval == NULL && pkg->vars)
     varval = g_strdup (g_hash_table_lookup (pkg->vars, var));
 
diff -up pkg-config-0.28/pkg-config.1.envvar pkg-config-0.28/pkg-config.1
--- pkg-config-0.28/pkg-config.1.envvar	2015-06-09 21:21:27.009637301 +0200
+++ pkg-config-0.28/pkg-config.1	2015-06-09 21:35:31.503400424 +0200
@@ -297,6 +297,11 @@ equal to /var/target (same rule apply to
 .TP
 .I "PKG_CONFIG_LIBDIR"
 Replaces the default \fIpkg-config\fP search directory, usually \fI/usr/lib/pkgconfig\fP
+.TP
+.I "PKG_CONFIG_$PACKAGE_$VARIABLE"
+Overrides the variable VARIABLE in the package PACKAGE. For example,
+setting PKG_CONFIG_GLADEUI_2_0_CATALOGDIR will override the
+variable "catalogdir" in the "gladeui-2.0" package.
 .\"
 .SH QUERYING PKG-CONFIG'S DEFAULTS
 .I pkg-config