diff --git a/ChangeLog b/ChangeLog
index 36614273..9b51fd57 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -9,8 +9,11 @@ found in the git revision history:
 * 3.4.1 (XXX)
 
   Bug fixes:
-  - Fix a Valgrind integration flaw that caused Valgrind warnings about reads of
-    uninitialized memory in arena chunk headers.
+  - Fix Valgrind integration flaws that caused Valgrind warnings about reads of
+    uninitialized memory in:
+    + arena chunk headers
+    + internal zero-initialized data structures (relevant to tcache and prof
+      code)
   - Preserve errno during the first allocation.  A readlink(2) call during
     initialization fails unless /etc/malloc.conf exists, so errno was typically
     set during the first allocation prior to this fix.
diff --git a/include/jemalloc/internal/tcache.h b/include/jemalloc/internal/tcache.h
index ba36204f..d4eecdee 100644
--- a/include/jemalloc/internal/tcache.h
+++ b/include/jemalloc/internal/tcache.h
@@ -313,6 +313,7 @@ tcache_alloc_small(tcache_t *tcache, size_t size, bool zero)
 			} else if (opt_zero)
 				memset(ret, 0, size);
 		}
+		VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 	} else {
 		if (config_fill && opt_junk) {
 			arena_alloc_junk_small(ret, &arena_bin_info[binind],
@@ -321,7 +322,6 @@ tcache_alloc_small(tcache_t *tcache, size_t size, bool zero)
 		VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 		memset(ret, 0, size);
 	}
-	VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 
 	if (config_stats)
 		tbin->tstats.nrequests++;
@@ -368,11 +368,11 @@ tcache_alloc_large(tcache_t *tcache, size_t size, bool zero)
 				else if (opt_zero)
 					memset(ret, 0, size);
 			}
+			VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 		} else {
 			VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 			memset(ret, 0, size);
 		}
-		VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 
 		if (config_stats)
 			tbin->tstats.nrequests++;
diff --git a/src/arena.c b/src/arena.c
index 0a73be2a..d28b629a 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -368,14 +368,21 @@ arena_run_zero(arena_chunk_t *chunk, size_t run_ind, size_t npages)
 	    (npages << LG_PAGE));
 }
 
+static inline void
+arena_run_page_mark_zeroed(arena_chunk_t *chunk, size_t run_ind)
+{
+
+	VALGRIND_MAKE_MEM_DEFINED((void *)((uintptr_t)chunk + (run_ind <<
+	    LG_PAGE)), PAGE);
+}
+
 static inline void
 arena_run_page_validate_zeroed(arena_chunk_t *chunk, size_t run_ind)
 {
 	size_t i;
 	UNUSED size_t *p = (size_t *)((uintptr_t)chunk + (run_ind << LG_PAGE));
 
-	VALGRIND_MAKE_MEM_DEFINED((void *)((uintptr_t)chunk + (run_ind <<
-	    LG_PAGE)), PAGE);
+	arena_run_page_mark_zeroed(chunk, run_ind);
 	for (i = 0; i < PAGE / sizeof(size_t); i++)
 		assert(p[i] == 0);
 }
@@ -458,6 +465,9 @@ arena_run_split(arena_t *arena, arena_run_t *run, size_t size, bool large,
 					} else if (config_debug) {
 						arena_run_page_validate_zeroed(
 						    chunk, run_ind+i);
+					} else {
+						arena_run_page_mark_zeroed(
+						    chunk, run_ind+i);
 					}
 				}
 			} else {
@@ -467,6 +477,9 @@ arena_run_split(arena_t *arena, arena_run_t *run, size_t size, bool large,
 				 */
 				arena_run_zero(chunk, run_ind, need_pages);
 			}
+		} else {
+			VALGRIND_MAKE_MEM_UNDEFINED((void *)((uintptr_t)chunk +
+			    (run_ind << LG_PAGE)), (need_pages << LG_PAGE));
 		}
 
 		/*
@@ -508,9 +521,9 @@ arena_run_split(arena_t *arena, arena_run_t *run, size_t size, bool large,
 			arena_run_page_validate_zeroed(chunk,
 			    run_ind+need_pages-1);
 		}
+		VALGRIND_MAKE_MEM_UNDEFINED((void *)((uintptr_t)chunk +
+		    (run_ind << LG_PAGE)), (need_pages << LG_PAGE));
 	}
-	VALGRIND_MAKE_MEM_UNDEFINED((void *)((uintptr_t)chunk + (run_ind <<
-	    LG_PAGE)), (need_pages << LG_PAGE));
 }
 
 static arena_chunk_t *
@@ -1465,6 +1478,7 @@ arena_malloc_small(arena_t *arena, size_t size, bool zero)
 			} else if (opt_zero)
 				memset(ret, 0, size);
 		}
+		VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 	} else {
 		if (config_fill && opt_junk) {
 			arena_alloc_junk_small(ret, &arena_bin_info[binind],
@@ -1473,7 +1487,6 @@ arena_malloc_small(arena_t *arena, size_t size, bool zero)
 		VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 		memset(ret, 0, size);
 	}
-	VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
 
 	return (ret);
 }