diff --git a/src/lib/Makefile.am b/src/lib/Makefile.am
index 5e9ebebae7..15c3a1a112 100644
--- a/src/lib/Makefile.am
+++ b/src/lib/Makefile.am
@@ -354,6 +354,7 @@ test_lib_SOURCES = \
 	test-llist.c \
 	test-log-throttle.c \
 	test-malloc-overflow.c \
+	test-mempool.c \
 	test-mempool-alloconly.c \
 	test-pkcs5.c \
 	test-net.c \
diff --git a/src/lib/test-lib.inc b/src/lib/test-lib.inc
index 8d54e3a220..7fb0b4a625 100644
--- a/src/lib/test-lib.inc
+++ b/src/lib/test-lib.inc
@@ -44,8 +44,10 @@ TEST(test_llist)
 TEST(test_log_throttle)
 TEST(test_malloc_overflow)
 FATAL(fatal_malloc_overflow)
-TEST(test_mempool_alloconly)
+TEST(test_mempool)
 FATAL(fatal_mempool)
+TEST(test_mempool_alloconly)
+FATAL(fatal_mempool_alloconly)
 TEST(test_net)
 TEST(test_numpack)
 TEST(test_ostream_escaped)
diff --git a/src/lib/test-mempool-alloconly.c b/src/lib/test-mempool-alloconly.c
index 99287011a1..6059bf5df0 100644
--- a/src/lib/test-mempool-alloconly.c
+++ b/src/lib/test-mempool-alloconly.c
@@ -53,13 +53,13 @@ void test_mempool_alloconly(void)
 	test_end();
 }
 
-enum fatal_test_state fatal_mempool(unsigned int stage)
+enum fatal_test_state fatal_mempool_alloconly(unsigned int stage)
 {
 	static pool_t pool;
 
 	switch(stage) {
 	case 0: /* forbidden size */
-		test_begin("fatal_mempool");
+		test_begin("fatal_mempool_alloconly");
 		pool = pool_alloconly_create(MEMPOOL_GROWING"fatal", 1);
 		(void)p_malloc(pool, 0);
 		return FATAL_TEST_FAILURE;
diff --git a/src/lib/test-mempool.c b/src/lib/test-mempool.c
new file mode 100644
index 0000000000..f909f59304
--- /dev/null
+++ b/src/lib/test-mempool.c
@@ -0,0 +1,144 @@
+/* Copyright (c) 2017 Dovecot authors, see the included COPYING file */
+
+#include "test-lib.h"
+
+#if SIZEOF_VOID_P == 8
+typedef char uint32max_array_t[4294967295];
+#else
+typedef char uint32max_array_t[65535];
+#endif
+
+extern struct pool test_pool;
+
+static void test_mempool_overflow(void)
+{
+	test_begin("mempool overflow");
+#if SIZEOF_VOID_P == 8
+	uint32max_array_t *m1 = p_new(&test_pool, uint32max_array_t, 4294967297ULL);
+	test_assert(m1 == POINTER_CAST(18446744073709551615ULL));
+	char *m2 = p_new(&test_pool, char, 18446744073709551615ULL);
+	test_assert(m2 == POINTER_CAST(18446744073709551615ULL));
+	uint32_t *m3 = p_new(&test_pool, uint32_t, 4611686018427387903ULL);
+	test_assert(m3 == POINTER_CAST(18446744073709551612ULL));
+
+	/* grow */
+	test_assert(p_realloc_type(&test_pool, m1, uint32max_array_t, 4294967296ULL, 4294967297ULL) == POINTER_CAST(18446744073709551615ULL));
+	test_assert(p_realloc_type(&test_pool, m2, char, 18446744073709551614ULL, 18446744073709551615ULL) == POINTER_CAST(18446744073709551615ULL));
+	test_assert(p_realloc_type(&test_pool, m3, uint32_t, 4611686018427387902ULL, 4611686018427387903ULL) == POINTER_CAST(18446744073709551612ULL));
+
+	/* shrink */
+	test_assert(p_realloc_type(&test_pool, m1, uint32max_array_t, 4294967297ULL, 4294967296ULL) == POINTER_CAST(18446744069414584320ULL));
+	test_assert(p_realloc_type(&test_pool, m2, char, 18446744073709551615ULL, 18446744073709551614ULL) == POINTER_CAST(18446744073709551614ULL));
+	test_assert(p_realloc_type(&test_pool, m3, uint32_t, 4611686018427387903ULL, 4611686018427387902ULL) == POINTER_CAST(18446744073709551608ULL));
+#elif SIZEOF_VOID_P == 4
+	uint32max_array_t *m1 = p_new(&test_pool, uint32max_array_t, 65537);
+	test_assert(m1 == POINTER_CAST(4294967295U));
+	char *m2 = p_new(&test_pool, char, 4294967295U);
+	test_assert(m2 == POINTER_CAST(4294967295U));
+	uint32_t *m3 = p_new(&test_pool, uint32_t, 1073741823U);
+	test_assert(m3 == POINTER_CAST(4294967292U));
+
+	/* grow */
+	test_assert(p_realloc_type(&test_pool, m1, uint32max_array_t, 65536, 65537) == POINTER_CAST(4294967295U));
+	test_assert(p_realloc_type(&test_pool, m2, char, 4294967294U, 4294967295U) == POINTER_CAST(4294967295U));
+	test_assert(p_realloc_type(&test_pool, m3, uint32_t, 1073741822U, 1073741823U) == POINTER_CAST(4294967292U));
+
+	/* shrink */
+	test_assert(p_realloc_type(&test_pool, m1, uint32max_array_t, 65537, 65536) == POINTER_CAST(4294901760U));
+	test_assert(p_realloc_type(&test_pool, m2, char, 4294967295U, 4294967294U) == POINTER_CAST(4294967294U));
+	test_assert(p_realloc_type(&test_pool, m3, uint32_t, 1073741823U, 1073741822U) == POINTER_CAST(4294967288U));
+#else
+#  error unsupported pointer size
+#endif
+	test_end();
+}
+
+enum fatal_test_state fatal_mempool(unsigned int stage)
+{
+	static uint32max_array_t *m1;
+	static uint32_t *m2;
+
+#if SIZEOF_VOID_P == 8
+	switch(stage) {
+	case 0:
+		test_begin("fatal mempool overflow");
+		m1 = p_new(&test_pool, uint32max_array_t, 4294967298ULL);
+		return FATAL_TEST_FAILURE;
+	case 1:
+		m2 = p_new(&test_pool, uint32_t, 4611686018427387904ULL);
+		return FATAL_TEST_FAILURE;
+	case 2: /* grow */
+		m1 = p_realloc_type(&test_pool, m1, uint32max_array_t, 4294967297ULL, 4294967298ULL);
+		return FATAL_TEST_FAILURE;
+	case 3:
+		m2 = p_realloc_type(&test_pool, m2, uint32_t, 4611686018427387903ULL, 4611686018427387904ULL);
+		return FATAL_TEST_FAILURE;
+	case 4: /* shrink */
+		m1 = p_realloc_type(&test_pool, m1, uint32max_array_t, 4294967298ULL, 4294967297ULL);
+		return FATAL_TEST_FAILURE;
+	case 5:
+		m2 = p_realloc_type(&test_pool, m2, uint32_t, 4611686018427387904ULL, 4611686018427387903ULL);
+		return FATAL_TEST_FAILURE;
+	}
+#elif SIZEOF_VOID_P == 4
+	switch(stage) {
+	case 0:
+		test_begin("fatal mempool overflow");
+		m1 = p_new(&test_pool, uint32max_array_t, 65538);
+		return FATAL_TEST_FAILURE;
+	case 1:
+		m2 = p_new(&test_pool, uint32_t, 1073741824U);
+		return FATAL_TEST_FAILURE;
+	case 2: /* grow */
+		m1 = p_realloc_type(&test_pool, m1, uint32max_array_t, 65537, 65538);
+		return FATAL_TEST_FAILURE;
+	case 3:
+		m2 = p_realloc_type(&test_pool, m2, uint32_t, 1073741823U, 1073741824U);
+		return FATAL_TEST_FAILURE;
+	case 4: /* shrink */
+		m1 = p_realloc_type(&test_pool, m1, uint32max_array_t, 65538, 65537);
+		return FATAL_TEST_FAILURE;
+	case 5:
+		m2 = p_realloc_type(&test_pool, m2, uint32_t, 1073741824U, 1073741823U);
+		return FATAL_TEST_FAILURE;
+	}
+#else
+#  error unsupported pointer size
+#endif
+	test_end();
+	return FATAL_TEST_FINISHED;
+}
+
+static const char *pool_test_get_name(pool_t pool ATTR_UNUSED) { return "test"; }
+static void pool_test_ref(pool_t pool ATTR_UNUSED) { }
+static void pool_test_unref(pool_t *pool) { *pool = NULL; }
+static void *pool_test_malloc(pool_t pool ATTR_UNUSED, size_t size) { return POINTER_CAST(size); }
+static void pool_test_free(pool_t pool ATTR_UNUSED, void *mem ATTR_UNUSED) { }
+static void *pool_test_realloc(pool_t pool ATTR_UNUSED, void *mem ATTR_UNUSED,
+			       size_t old_size ATTR_UNUSED, size_t new_size) {
+	return POINTER_CAST(new_size);
+}
+static void pool_test_clear(pool_t pool ATTR_UNUSED) { }
+static size_t pool_test_get_max_easy_alloc_size(pool_t pool ATTR_UNUSED) { return 12345; }
+static const struct pool_vfuncs test_pool_vfuncs = {
+	pool_test_get_name,
+	pool_test_ref,
+	pool_test_unref,
+	pool_test_malloc,
+	pool_test_free,
+	pool_test_realloc,
+	pool_test_clear,
+	pool_test_get_max_easy_alloc_size
+};
+
+struct pool test_pool = {
+	.v = &test_pool_vfuncs,
+
+	.alloconly_pool = TRUE,
+	.datastack_pool = FALSE,
+};
+
+void test_mempool(void)
+{
+	test_mempool_overflow();
+}