diff --git a/configure.ac b/configure.ac
index ca7a323e91..a87fb3f2b5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -422,7 +422,7 @@ else
   if test "x$enable_debug" = "xno"; then
     GTK_DEBUG_FLAGS="-DG_DISABLE_ASSERT -DG_DISABLE_CHECKS -DG_DISABLE_CAST_CHECKS"
   else
-    GTK_DEBUG_FLAGS="-DG_DISABLE_CAST_CHECKS"
+    GTK_DEBUG_FLAGS="-DG_ENABLE_DEBUG -DG_DISABLE_CAST_CHECKS"
   fi
 fi
 
diff --git a/docs/reference/gtk/running.sgml b/docs/reference/gtk/running.sgml
index 147637e42d..fe91aead74 100644
--- a/docs/reference/gtk/running.sgml
+++ b/docs/reference/gtk/running.sgml
@@ -58,8 +58,8 @@ warning that occurs.
 <para>
 A list of <link linkend="GTK-Debug-Options">debug options</link>
 to turn on in addition to those specified in the <envar>GTK_DEBUG</envar>
-environment variable. This option is only available if GTK+ has been
-configured with <option>--enable-debug=yes</option>.
+environment variable. This option is not available if GTK+ has been
+configured with <option>--enable-debug=no</option>.
 </para>
 </formalpara>
 
@@ -134,7 +134,7 @@ additional environment variables.
   <title><envar>GTK_DEBUG</envar></title>
 
   <para>
-  If GTK+ has been configured with <option>--enable-debug=yes</option>,
+  Unless GTK+ has been configured with <option>--enable-debug=no</option>,
   this variable can be set to a list of debug options, which cause GTK+
   to print out different types of debugging information.
   <variablelist>