diff --git a/gobject/gtype.c b/gobject/gtype.c
index 40953843d..66db7bc9d 100644
--- a/gobject/gtype.c
+++ b/gobject/gtype.c
@@ -1824,6 +1824,18 @@ type_iface_blow_holder_info_Wm (TypeNode *iface,
     }
 }
 
+/* We use the system allocator on UNIX-y systems, where we know we have
+ * access to a decent allocator. On other systems, we fall back to the
+ * slice allocator, as we know its performance profile
+ */
+#ifdef G_OS_UNIX
+# define instance_alloc(s)  g_malloc0 ((s))
+# define instance_free(s,p) g_free ((p))
+#else
+# define instance_alloc(s)  g_slice_alloc0 ((s))
+# define instance_free(s,p) g_slice_free1 ((s),(p))
+#endif
+
 /**
  * g_type_create_instance: (skip)
  * @type: an instantiatable type to create an instance for
@@ -1900,7 +1912,7 @@ g_type_create_instance (GType type)
       private_size += ALIGN_STRUCT (1);
 
       /* Allocate one extra pointer size... */
-      allocated = g_slice_alloc0 (private_size + ivar_size + sizeof (gpointer));
+      allocated = instance_alloc (private_size + ivar_size + sizeof (gpointer));
       /* ... and point it back to the start of the private data. */
       *(gpointer *) (allocated + private_size + ivar_size) = allocated + ALIGN_STRUCT (1);
 
@@ -1910,7 +1922,7 @@ g_type_create_instance (GType type)
     }
   else
 #endif
-    allocated = g_slice_alloc0 (private_size + ivar_size);
+    allocated = instance_alloc (private_size + ivar_size);
 
   instance = (GTypeInstance *) (allocated + private_size);
 
@@ -2000,14 +2012,14 @@ g_type_free_instance (GTypeInstance *instance)
       /* Clear out the extra pointer... */
       *(gpointer *) (allocated + private_size + ivar_size) = NULL;
       /* ... and ensure we include it in the size we free. */
-      g_slice_free1 (private_size + ivar_size + sizeof (gpointer), allocated);
+      instance_free (private_size + ivar_size + sizeof (gpointer), allocated);
 
       VALGRIND_FREELIKE_BLOCK (allocated + ALIGN_STRUCT (1), 0);
       VALGRIND_FREELIKE_BLOCK (instance, 0);
     }
   else
 #endif
-    g_slice_free1 (private_size + ivar_size, allocated);
+    instance_free (private_size + ivar_size, allocated);
 
 #ifdef	G_ENABLE_DEBUG
   IF_DEBUG (INSTANCE_COUNT)