diff --git a/phosphor-regulators/docs/config_file/compare_vpd.md b/phosphor-regulators/docs/config_file/compare_vpd.md
index 79927c1..304bfcf 100644
--- a/phosphor-regulators/docs/config_file/compare_vpd.md
+++ b/phosphor-regulators/docs/config_file/compare_vpd.md
@@ -7,6 +7,10 @@
 from an EEPROM on a Field-Replaceable Unit (FRU).  For this reason, VPD is also
 called "FRU data".
 
+The phosphor-regulators application obtains VPD keyword values from D-Bus.
+Other BMC applications and drivers are responsible for reading VPD from
+hardware components and publishing it on D-Bus.
+
 The following VPD keywords are currently supported:
 * CCIN
 * Manufacturer
@@ -18,13 +22,28 @@
 a VPD keyword value.  For example, you could set the output voltage only for
 regulators with a specific Model number.
 
+### Unavailable keyword values
+A keyword value may be unavailable if:
+* The hardware component does not support the keyword.
+* An error occurred while attempting to read VPD from the hardware component.
+* The BMC cannot access the VPD due to the system hardware design, such as not
+  being connected to the necessary I2C bus.
+
+If the keyword value is unavailable, it will be treated as having an "empty"
+value:
+* An empty string ("") if the "value" property was specified.
+* An empty array ([]) if the "byte_values" property was specified.
+
+If the expected value is not "empty", the compare_vpd action will return false
+since the values will not match.
+
 ## Properties
 | Name | Required | Type | Description |
 | :--- | :------: | :--- | :---------- |
 | fru | yes | string | Field-Replaceable Unit (FRU) that contains the VPD.  Specify the relative D-Bus inventory path of the FRU.  Full inventory paths begin with the root "/xyz/openbmc_project/inventory".  Specify the relative path below the root, such as "system/chassis/disk_backplane". |
 | keyword | yes | string | VPD keyword.  Specify one of the following: "CCIN", "Manufacturer", "Model", "PartNumber", "HW". |
 | value | see [notes](#notes) | string | Expected value. |
-| byte\_values | see [notes](#notes) | array of strings | One or more expected byte values expressed in hexadecimal.  Each value must be prefixed with 0x and surrounded by double quotes. |
+| byte\_values | see [notes](#notes) | array of strings | Zero or more expected byte values expressed in hexadecimal.  Each value must be prefixed with 0x and surrounded by double quotes. |
 
 ### Notes
 * You must specify either "value" or "byte_values".
diff --git a/phosphor-regulators/schema/config_schema.json b/phosphor-regulators/schema/config_schema.json
index 2e0a8b7..dbfed58 100644
--- a/phosphor-regulators/schema/config_schema.json
+++ b/phosphor-regulators/schema/config_schema.json
@@ -133,7 +133,7 @@
                 "fru": {"$ref": "#/definitions/inventory_path" },
                 "keyword": {"$ref": "#/definitions/keyword" },
                 "value": {"$ref": "#/definitions/string_value" },
-                "byte_values": {"$ref": "#/definitions/bytes_values" }
+                "byte_values": {"$ref": "#/definitions/byte_values_min0" }
             },
             "required": ["fru", "keyword"],
             "oneOf": [
@@ -236,21 +236,28 @@
             "properties":
             {
                 "register": {"$ref": "#/definitions/register" },
-                "values": {"$ref": "#/definitions/bytes_values" },
-                "masks": {"$ref": "#/definitions/bytes_masks" }
+                "values": {"$ref": "#/definitions/byte_values" },
+                "masks": {"$ref": "#/definitions/byte_masks" }
             },
             "required": ["register", "values"],
             "additionalProperties": false
         },
 
-        "bytes_values":
+        "byte_values":
         {
             "type": "array",
             "items": {"$ref": "#/definitions/byte_value" },
             "minItems": 1
         },
 
-        "bytes_masks":
+        "byte_values_min0":
+        {
+            "type": "array",
+            "items": {"$ref": "#/definitions/byte_value" },
+            "minItems": 0
+        },
+
+        "byte_masks":
         {
             "type": "array",
             "items": {"$ref": "#/definitions/byte_mask" },
diff --git a/phosphor-regulators/src/config_file_parser.cpp b/phosphor-regulators/src/config_file_parser.cpp
index db0cd7a..3eecbb6 100644
--- a/phosphor-regulators/src/config_file_parser.cpp
+++ b/phosphor-regulators/src/config_file_parser.cpp
@@ -287,7 +287,7 @@
     auto byteValuesIt = element.find("byte_values");
     if ((valueIt != element.end()) && (byteValuesIt == element.end()))
     {
-        std::string stringValue = parseString(*valueIt);
+        std::string stringValue = parseString(*valueIt, true);
         value.insert(value.begin(), stringValue.begin(), stringValue.end());
         ++propertyCount;
     }
diff --git a/phosphor-regulators/test/actions/compare_vpd_action_tests.cpp b/phosphor-regulators/test/actions/compare_vpd_action_tests.cpp
index 26361b9..c90c09e 100644
--- a/phosphor-regulators/test/actions/compare_vpd_action_tests.cpp
+++ b/phosphor-regulators/test/actions/compare_vpd_action_tests.cpp
@@ -36,19 +36,36 @@
 
 TEST(CompareVPDActionTests, Constructor)
 {
-    std::vector<uint8_t> value{0x32, 0x44, 0x33, 0x35}; // "2D35"
-    CompareVPDAction action{
-        "/xyz/openbmc_project/inventory/system/chassis/disk_backplane", "CCIN",
-        value};
-    EXPECT_EQ(action.getFRU(),
-              "/xyz/openbmc_project/inventory/system/chassis/disk_backplane");
-    EXPECT_EQ(action.getKeyword(), "CCIN");
-    EXPECT_EQ(action.getValue(), value);
+    // Value vector is not empty
+    {
+        std::vector<uint8_t> value{0x32, 0x44, 0x33, 0x35}; // "2D35"
+        CompareVPDAction action{
+            "/xyz/openbmc_project/inventory/system/chassis/disk_backplane",
+            "CCIN", value};
+        EXPECT_EQ(
+            action.getFRU(),
+            "/xyz/openbmc_project/inventory/system/chassis/disk_backplane");
+        EXPECT_EQ(action.getKeyword(), "CCIN");
+        EXPECT_EQ(action.getValue(), value);
+    }
+
+    // Value vector is empty
+    {
+        std::vector<uint8_t> value{};
+        CompareVPDAction action{
+            "/xyz/openbmc_project/inventory/system/chassis/disk_backplane",
+            "CCIN", value};
+        EXPECT_EQ(
+            action.getFRU(),
+            "/xyz/openbmc_project/inventory/system/chassis/disk_backplane");
+        EXPECT_EQ(action.getKeyword(), "CCIN");
+        EXPECT_EQ(action.getValue(), value);
+    }
 }
 
 TEST(CompareVPDActionTests, Execute)
 {
-    // Test where works: Actual VPD value is not an empty string
+    // Test where works: Actual VPD value is not empty
     {
         std::string fru{"/xyz/openbmc_project/inventory/system"};
         std::string keyword{"Model"};
@@ -85,13 +102,13 @@
         }
     }
 
-    // Test where works: Actual VPD value is an empty string
+    // Test where works: Actual VPD value is empty
     {
         std::string fru{"/xyz/openbmc_project/inventory/system"};
         std::string keyword{"Model"};
         std::vector<uint8_t> emptyValue{};
 
-        // Create MockServices object.  VPD service will return "" as VPD value
+        // Create MockServices object.  VPD service will return empty VPD value
         // 2 times.
         MockServices services{};
         MockVPD& vpd = services.getMockVPD();
@@ -194,6 +211,7 @@
 
 TEST(CompareVPDActionTests, ToString)
 {
+    // Test where value vector is not empty
     {
         CompareVPDAction action{
             "/xyz/openbmc_project/inventory/system/chassis/disk_backplane",
@@ -204,6 +222,7 @@
                                      "CCIN, value: [ 0x1, 0xA3, 0x0, 0xFF ] }");
     }
 
+    // Test where value vector is empty
     {
         CompareVPDAction action{
             "/xyz/openbmc_project/inventory/system/chassis/disk_backplane",
diff --git a/phosphor-regulators/test/config_file_parser_tests.cpp b/phosphor-regulators/test/config_file_parser_tests.cpp
index 38bee22..f477d41 100644
--- a/phosphor-regulators/test/config_file_parser_tests.cpp
+++ b/phosphor-regulators/test/config_file_parser_tests.cpp
@@ -1138,7 +1138,7 @@
 
 TEST(ConfigFileParserTests, ParseCompareVPD)
 {
-    // Test where works, using "value"
+    // Test where works: value property: Not empty
     {
         const json element = R"(
             {
@@ -1156,7 +1156,24 @@
                   (std::vector<uint8_t>{0x32, 0x44, 0x33, 0x35}));
     }
 
-    // Test where works, using "byte_values"
+    // Test where works: value property: Empty
+    {
+        const json element = R"(
+            {
+              "fru": "system/chassis/disk_backplane",
+              "keyword": "CCIN",
+              "value": ""
+            }
+        )"_json;
+        std::unique_ptr<CompareVPDAction> action = parseCompareVPD(element);
+        EXPECT_EQ(
+            action->getFRU(),
+            "/xyz/openbmc_project/inventory/system/chassis/disk_backplane");
+        EXPECT_EQ(action->getKeyword(), "CCIN");
+        EXPECT_EQ(action->getValue(), (std::vector<uint8_t>{}));
+    }
+
+    // Test where works: byte_values property: Not empty
     {
         const json element = R"(
             {
@@ -1173,6 +1190,23 @@
         EXPECT_EQ(action->getValue(), (std::vector<uint8_t>{0x11, 0x22, 0x33}));
     }
 
+    // Test where works: byte_values property: Empty
+    {
+        const json element = R"(
+            {
+              "fru": "system/chassis/disk_backplane",
+              "keyword": "CCIN",
+              "byte_values": []
+            }
+        )"_json;
+        std::unique_ptr<CompareVPDAction> action = parseCompareVPD(element);
+        EXPECT_EQ(
+            action->getFRU(),
+            "/xyz/openbmc_project/inventory/system/chassis/disk_backplane");
+        EXPECT_EQ(action->getKeyword(), "CCIN");
+        EXPECT_EQ(action->getValue(), (std::vector<uint8_t>{}));
+    }
+
     // Test where fails: Element is not an object
     try
     {
@@ -1256,7 +1290,7 @@
                                "either value or byte_values");
     }
 
-    // Test where fails: both value and byte_value specified
+    // Test where fails: both value and byte_values specified
     try
     {
         const json element = R"(
diff --git a/phosphor-regulators/test/validate-regulators-config_tests.cpp b/phosphor-regulators/test/validate-regulators-config_tests.cpp
index f6033d5..2763cc9 100644
--- a/phosphor-regulators/test/validate-regulators-config_tests.cpp
+++ b/phosphor-regulators/test/validate-regulators-config_tests.cpp
@@ -702,12 +702,20 @@
     compareVpdFile["rules"][0]["actions"][1]["compare_vpd"]["keyword"] = "CCIN";
     compareVpdFile["rules"][0]["actions"][1]["compare_vpd"]["value"] = "2D35";
 
-    // Valid.
+    // Valid: value property: not empty.
     {
         json configFile = compareVpdFile;
         EXPECT_JSON_VALID(configFile);
     }
-    // Valid, using byte_values.
+
+    // Valid: value property: empty.
+    {
+        json configFile = compareVpdFile;
+        configFile["rules"][0]["actions"][1]["compare_vpd"]["value"] = "";
+        EXPECT_JSON_VALID(configFile);
+    }
+
+    // Valid: byte_values property: not empty.
     {
         json configFile = compareVpdFile;
         configFile["rules"][0]["actions"][1]["compare_vpd"].erase("value");
@@ -716,6 +724,15 @@
         EXPECT_JSON_VALID(configFile);
     }
 
+    // Valid: byte_values property: empty.
+    {
+        json configFile = compareVpdFile;
+        configFile["rules"][0]["actions"][1]["compare_vpd"].erase("value");
+        configFile["rules"][0]["actions"][1]["compare_vpd"]["byte_values"] =
+            json::array();
+        EXPECT_JSON_VALID(configFile);
+    }
+
     // Invalid: no FRU property.
     {
         json configFile = compareVpdFile;
@@ -785,16 +802,6 @@
                             "'0x50' is not of type 'array'");
     }
 
-    // Invalid: property byte_values is empty
-    {
-        json configFile = compareVpdFile;
-        configFile["rules"][0]["actions"][1]["compare_vpd"].erase("value");
-        configFile["rules"][0]["actions"][1]["compare_vpd"]["byte_values"] =
-            json::array();
-        EXPECT_JSON_INVALID(configFile, "Validation failed.",
-                            "[] is too short");
-    }
-
     // Invalid: properties byte_values and value both exist
     {
         json configFile = compareVpdFile;