diff --git a/src/box/field_map.h b/src/box/field_map.h
index b0dfeb4e4579a5d7ea549bdee8d5dc9fb18cd4ae..a1a5a9dba820d577977260bfc2e1b4b1df0b8b9f 100644
--- a/src/box/field_map.h
+++ b/src/box/field_map.h
@@ -152,8 +152,8 @@ field_map_get_offset(const uint32_t *field_map, int32_t offset_slot,
 		     int multikey_idx)
 {
 	uint32_t offset;
-	if (multikey_idx != MULTIKEY_NONE && field_map[offset_slot] > 0) {
-		assert((int32_t)field_map[offset_slot] < 0);
+	if (multikey_idx != MULTIKEY_NONE &&
+	    (int32_t) field_map[offset_slot] < 0) {
 		/**
 		 * The field_map extent has the following
 		 * structure: [size=N|slot1|slot2|..|slotN]
diff --git a/test/engine/multikey.result b/test/engine/multikey.result
index 1d5d9e20095d4ee6b1ab8ba96bbc0d859fc91cc9..38c108ebc305e22fd1f5b3a4b107d5eb29b365ca 100644
--- a/test/engine/multikey.result
+++ b/test/engine/multikey.result
@@ -753,3 +753,27 @@ i2:select()
 s:drop()
 ---
 ...
+--
+-- gh-4234: Assert when using indexes containing both multikey
+--          and regular key_parts.
+--
+s = box.schema.space.create('clients', {engine = engine})
+---
+...
+name_idx = s:create_index('name_idx', {parts = {{1, 'string'}}})
+---
+...
+phone_idx = s:create_index('phone_idx', {parts = {{'[2][*]', 'string'}, {3, 'string'}}, unique=false})
+---
+...
+s:insert({"Genadiy", {"911"}, 'b'})
+---
+- ['Genadiy', ['911'], 'b']
+...
+s:insert({"Jorge", {"911", "89457609234"}, 'a'})
+---
+- ['Jorge', ['911', '89457609234'], 'a']
+...
+s:drop()
+---
+...
diff --git a/test/engine/multikey.test.lua b/test/engine/multikey.test.lua
index f32f49d2b993e9c5f0f6946d273d2c5f39d60ab5..a2bef989f93db8b387366a95234ef3a2ab566e25 100644
--- a/test/engine/multikey.test.lua
+++ b/test/engine/multikey.test.lua
@@ -194,3 +194,14 @@ s:replace{2, {{2, 3}}}
 i2 = s:create_index('sk', {parts = {{2, 'unsigned', path = '[1][*]'}}})
 i2:select()
 s:drop()
+
+--
+-- gh-4234: Assert when using indexes containing both multikey
+--          and regular key_parts.
+--
+s = box.schema.space.create('clients', {engine = engine})
+name_idx = s:create_index('name_idx', {parts = {{1, 'string'}}})
+phone_idx = s:create_index('phone_idx', {parts = {{'[2][*]', 'string'}, {3, 'string'}}, unique=false})
+s:insert({"Genadiy", {"911"}, 'b'})
+s:insert({"Jorge", {"911", "89457609234"}, 'a'})
+s:drop()