diff --git a/Makefile.in b/Makefile.in
index ba0c80b6..008cffd8 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -204,6 +204,7 @@ TESTS_UNIT := \
 	$(srcroot)test/unit/counter.c \
 	$(srcroot)test/unit/decay.c \
 	$(srcroot)test/unit/div.c \
+	$(srcroot)test/unit/double_free.c \
 	$(srcroot)test/unit/edata_cache.c \
 	$(srcroot)test/unit/emitter.c \
 	$(srcroot)test/unit/extent_quantize.c \
@@ -308,7 +309,6 @@ TESTS_STRESS := $(srcroot)test/stress/batch_alloc.c \
 	$(srcroot)test/stress/large_microbench.c \
 	$(srcroot)test/stress/mallctl.c \
 	$(srcroot)test/stress/microbench.c
-	
 
 
 TESTS := $(TESTS_UNIT) $(TESTS_INTEGRATION) $(TESTS_INTEGRATION_CPP) \
diff --git a/include/jemalloc/internal/arena_inlines_b.h b/include/jemalloc/internal/arena_inlines_b.h
index 335c0797..7971b4c7 100644
--- a/include/jemalloc/internal/arena_inlines_b.h
+++ b/include/jemalloc/internal/arena_inlines_b.h
@@ -5,6 +5,7 @@
 #include "jemalloc/internal/jemalloc_internal_types.h"
 #include "jemalloc/internal/mutex.h"
 #include "jemalloc/internal/rtree.h"
+#include "jemalloc/internal/safety_check.h"
 #include "jemalloc/internal/sc.h"
 #include "jemalloc/internal/sz.h"
 #include "jemalloc/internal/ticker.h"
@@ -203,6 +204,32 @@ arena_vsalloc(tsdn_t *tsdn, const void *ptr) {
 	return sz_index2size(full_alloc_ctx.szind);
 }
 
+JEMALLOC_ALWAYS_INLINE bool
+large_dalloc_safety_checks(edata_t *edata, szind_t szind) {
+	if (!config_opt_safety_checks) {
+		return false;
+	}
+
+	/*
+	 * Eagerly detect double free and sized dealloc bugs for large sizes.
+	 * The cost is low enough (as edata will be accessed anyway) to be
+	 * enabled all the time.
+	 */
+	if (unlikely(edata_state_get(edata) != extent_state_active)) {
+		safety_check_fail("Invalid deallocation detected: "
+		    "pages being freed (%p) not currently active, "
+		    "possibly caused by double free bugs.",
+		    (uintptr_t)edata_addr_get(edata));
+		return true;
+	}
+	if (unlikely(sz_index2size(szind) != edata_usize_get(edata))) {
+		safety_check_fail_sized_dealloc(/* current_dealloc */ true);
+		return true;
+	}
+
+	return false;
+}
+
 static inline void
 arena_dalloc_large_no_tcache(tsdn_t *tsdn, void *ptr, szind_t szind) {
 	if (config_prof && unlikely(szind < SC_NBINS)) {
@@ -210,6 +237,10 @@ arena_dalloc_large_no_tcache(tsdn_t *tsdn, void *ptr, szind_t szind) {
 	} else {
 		edata_t *edata = emap_edata_lookup(tsdn, &arena_emap_global,
 		    ptr);
+		if (large_dalloc_safety_checks(edata, szind)) {
+			/* See the comment in isfree. */
+			return;
+		}
 		large_dalloc(tsdn, edata);
 	}
 }
@@ -250,6 +281,10 @@ arena_dalloc_large(tsdn_t *tsdn, void *ptr, tcache_t *tcache, szind_t szind,
 	} else {
 		edata_t *edata = emap_edata_lookup(tsdn, &arena_emap_global,
 		    ptr);
+		if (large_dalloc_safety_checks(edata, szind)) {
+			/* See the comment in isfree. */
+			return;
+		}
 		large_dalloc(tsdn, edata);
 	}
 }
diff --git a/src/jemalloc.c b/src/jemalloc.c
index bbf62555..1d6191ae 100644
--- a/src/jemalloc.c
+++ b/src/jemalloc.c
@@ -2812,7 +2812,7 @@ maybe_check_alloc_ctx(tsd_t *tsd, void *ptr, emap_alloc_ctx_t *alloc_ctx) {
 		    &dbg_ctx);
 		if (alloc_ctx->szind != dbg_ctx.szind) {
 			safety_check_fail_sized_dealloc(
-			    /* curent_dealloc */ true);
+			    /* current_dealloc */ true);
 			return true;
 		}
 		if (alloc_ctx->slab != dbg_ctx.slab) {
diff --git a/src/tcache.c b/src/tcache.c
index 90ca372e..06efe66a 100644
--- a/src/tcache.c
+++ b/src/tcache.c
@@ -428,6 +428,10 @@ tcache_bin_flush_impl(tsd_t *tsd, tcache_t *tcache, cache_bin_t *cache_bin,
 					dalloc_count++;
 				}
 			} else {
+				if (large_dalloc_safety_checks(edata, binind)) {
+					/* See the comment in isfree. */
+					continue;
+				}
 				large_dalloc_finish(tsdn, edata);
 			}
 		}
diff --git a/test/unit/double_free.c b/test/unit/double_free.c
new file mode 100644
index 00000000..73155b9c
--- /dev/null
+++ b/test/unit/double_free.c
@@ -0,0 +1,56 @@
+#include "test/jemalloc_test.h"
+
+#include "jemalloc/internal/safety_check.h"
+
+bool fake_abort_called;
+void fake_abort(const char *message) {
+	(void)message;
+	fake_abort_called = true;
+}
+
+void
+test_large_double_free_pre(void) {
+	safety_check_set_abort(&fake_abort);
+	fake_abort_called = false;
+}
+
+void
+test_large_double_free_post() {
+	expect_b_eq(fake_abort_called, true, "Double-free check didn't fire.");
+	safety_check_set_abort(NULL);
+}
+
+TEST_BEGIN(test_large_double_free_tcache) {
+	test_skip_if(!config_opt_safety_checks);
+	/*
+	 * Skip debug builds, since too many assertions will be triggered with
+	 * double-free before hitting the one we are interested in.
+	 */
+	test_skip_if(config_debug);
+
+	test_large_double_free_pre();
+	char *ptr = malloc(SC_LARGE_MINCLASS);
+	free(ptr);
+	free(ptr);
+	mallctl("thread.tcache.flush", NULL, NULL, NULL, 0);
+	test_large_double_free_post();
+}
+TEST_END
+
+TEST_BEGIN(test_large_double_free_no_tcache) {
+	test_skip_if(!config_opt_safety_checks);
+	test_skip_if(config_debug);
+
+	test_large_double_free_pre();
+	char *ptr = mallocx(SC_LARGE_MINCLASS, MALLOCX_TCACHE_NONE);
+	dallocx(ptr, MALLOCX_TCACHE_NONE);
+	dallocx(ptr, MALLOCX_TCACHE_NONE);
+	test_large_double_free_post();
+}
+TEST_END
+
+int
+main(void) {
+	return test(test_large_double_free_no_tcache,
+	    test_large_double_free_tcache);
+}
diff --git a/test/unit/double_free.h b/test/unit/double_free.h
new file mode 100644
index 00000000..8b137891
--- /dev/null
+++ b/test/unit/double_free.h
@@ -0,0 +1 @@
+
diff --git a/test/unit/size_check.c b/test/unit/size_check.c
index 3d2912df..accdc405 100644
--- a/test/unit/size_check.c
+++ b/test/unit/size_check.c
@@ -8,48 +8,65 @@ void fake_abort(const char *message) {
 	fake_abort_called = true;
 }
 
-#define SIZE1 SC_SMALL_MAXCLASS
-#define SIZE2 (SC_SMALL_MAXCLASS / 2)
+#define SMALL_SIZE1 SC_SMALL_MAXCLASS
+#define SMALL_SIZE2 (SC_SMALL_MAXCLASS / 2)
 
-TEST_BEGIN(test_invalid_size_sdallocx) {
-	test_skip_if(!config_opt_size_checks);
+#define LARGE_SIZE1 SC_LARGE_MINCLASS
+#define LARGE_SIZE2 (LARGE_SIZE1 * 2)
+
+void *
+test_invalid_size_pre(size_t sz) {
 	safety_check_set_abort(&fake_abort);
 
 	fake_abort_called = false;
-	void *ptr = malloc(SIZE1);
+	void *ptr = malloc(sz);
 	assert_ptr_not_null(ptr, "Unexpected failure");
-	sdallocx(ptr, SIZE2, 0);
-	expect_true(fake_abort_called, "Safety check didn't fire");
 
+	return ptr;
+}
+
+void
+test_invalid_size_post(void) {
+	expect_true(fake_abort_called, "Safety check didn't fire");
 	safety_check_set_abort(NULL);
 }
+
+TEST_BEGIN(test_invalid_size_sdallocx) {
+	test_skip_if(!config_opt_size_checks);
+
+	void *ptr = test_invalid_size_pre(SMALL_SIZE1);
+	sdallocx(ptr, SMALL_SIZE2, 0);
+	test_invalid_size_post();
+
+	ptr = test_invalid_size_pre(LARGE_SIZE1);
+	sdallocx(ptr, LARGE_SIZE2, 0);
+	test_invalid_size_post();
+}
 TEST_END
 
 TEST_BEGIN(test_invalid_size_sdallocx_nonzero_flag) {
 	test_skip_if(!config_opt_size_checks);
-	safety_check_set_abort(&fake_abort);
 
-	fake_abort_called = false;
-	void *ptr = malloc(SIZE1);
-	assert_ptr_not_null(ptr, "Unexpected failure");
-	sdallocx(ptr, SIZE2, MALLOCX_TCACHE_NONE);
-	expect_true(fake_abort_called, "Safety check didn't fire");
+	void *ptr = test_invalid_size_pre(SMALL_SIZE1);
+	sdallocx(ptr, SMALL_SIZE2, MALLOCX_TCACHE_NONE);
+	test_invalid_size_post();
 
-	safety_check_set_abort(NULL);
+	ptr = test_invalid_size_pre(LARGE_SIZE1);
+	sdallocx(ptr, LARGE_SIZE2, MALLOCX_TCACHE_NONE);
+	test_invalid_size_post();
 }
 TEST_END
 
 TEST_BEGIN(test_invalid_size_sdallocx_noflags) {
 	test_skip_if(!config_opt_size_checks);
-	safety_check_set_abort(&fake_abort);
 
-	fake_abort_called = false;
-	void *ptr = malloc(SIZE1);
-	assert_ptr_not_null(ptr, "Unexpected failure");
-	je_sdallocx_noflags(ptr, SIZE2);
-	expect_true(fake_abort_called, "Safety check didn't fire");
+	void *ptr = test_invalid_size_pre(SMALL_SIZE1);
+	je_sdallocx_noflags(ptr, SMALL_SIZE2);
+	test_invalid_size_post();
 
-	safety_check_set_abort(NULL);
+	ptr = test_invalid_size_pre(LARGE_SIZE1);
+	je_sdallocx_noflags(ptr, LARGE_SIZE2);
+	test_invalid_size_post();
 }
 TEST_END