diff --git a/ChangeLog b/ChangeLog
index c8865059..80a21e79 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -12,6 +12,10 @@ found in the git revision history:
   - Auto-detect whether running inside Valgrind, thus removing the need to
     manually specify MALLOC_CONF=valgrind:true.
 
+  Incompatible changes:
+  - Disable tcache by default if running inside Valgrind, in order to avoid
+    making unallocated objects appear reachable to Valgrind.
+
   Bug fixes:
   - Fix heap profiling crash if sampled object is freed via realloc(p, 0).
 
diff --git a/doc/jemalloc.xml.in b/doc/jemalloc.xml.in
index 8a13a22c..b34467be 100644
--- a/doc/jemalloc.xml.in
+++ b/doc/jemalloc.xml.in
@@ -969,7 +969,8 @@ malloc_conf = "xmalloc:true";]]></programlisting>
         <link
         linkend="opt.lg_tcache_max"><mallctl>opt.lg_tcache_max</mallctl></link>
         option for related tuning information.  This option is enabled by
-        default.</para></listitem>
+        default unless running inside <ulink
+        url="http://valgrind.org/">Valgrind</ulink>.</para></listitem>
       </varlistentry>
 
       <varlistentry id="opt.lg_tcache_max">
diff --git a/src/jemalloc.c b/src/jemalloc.c
index 77ea8c81..481936dc 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -389,6 +389,8 @@ malloc_conf_init(void)
 			opt_quarantine = JEMALLOC_VALGRIND_QUARANTINE_DEFAULT;
 			opt_redzone = true;
 		}
+		if (config_tcache && opt_valgrind)
+			opt_tcache = false;
 	}
 
 	for (i = 0; i < 3; i++) {