diff --git a/src/command/backup/option.c.inc b/src/command/backup/option.c.inc
index b2639e343..dba282d39 100644
--- a/src/command/backup/option.c.inc
+++ b/src/command/backup/option.c.inc
@@ -47,11 +47,11 @@ static const ManifestBlockIncrMap manifestBlockIncrMap =
 
 // Convert map size
 static unsigned int
-backupBlockIncrMapSize(const ConfigOption optionId, const unsigned int optionKeyIdx, const String *const value)
+backupBlockIncrMapSize(const ConfigOption optionId, const unsigned int optionIdx, const String *const value)
 {
     FUNCTION_TEST_BEGIN();
         FUNCTION_TEST_PARAM(ENUM, optionId);
-        FUNCTION_TEST_PARAM(UINT, optionKeyIdx);
+        FUNCTION_TEST_PARAM(UINT, optionIdx);
         FUNCTION_TEST_PARAM(STRING, value);
     FUNCTION_TEST_END();
 
@@ -69,7 +69,7 @@ backupBlockIncrMapSize(const ConfigOption optionId, const unsigned int optionKey
     {
         THROW_FMT(
             OptionInvalidValueError, "'%s' is not valid for '%s' option", strZ(value),
-            cfgParseOptionKeyIdxName(optionId, optionKeyIdx));
+            cfgOptionIdxName(optionId, optionIdx));
     }
     TRY_END();
 
@@ -80,11 +80,11 @@ backupBlockIncrMapSize(const ConfigOption optionId, const unsigned int optionKey
 
 // Convert map checksum size
 static unsigned int
-backupBlockIncrMapChecksumSize(const ConfigOption optionId, const unsigned int optionKeyIdx, const Variant *const value)
+backupBlockIncrMapChecksumSize(const ConfigOption optionId, const unsigned int optionIdx, const Variant *const value)
 {
     FUNCTION_TEST_BEGIN();
         FUNCTION_TEST_PARAM(ENUM, optionId);
-        FUNCTION_TEST_PARAM(UINT, optionKeyIdx);
+        FUNCTION_TEST_PARAM(UINT, optionIdx);
         FUNCTION_TEST_PARAM(VARIANT, value);
     FUNCTION_TEST_END();
 
@@ -103,7 +103,7 @@ backupBlockIncrMapChecksumSize(const ConfigOption optionId, const unsigned int o
     {
         THROW_FMT(
             OptionInvalidValueError, "'%s' is not valid for '%s' option", strZ(varStr(value)),
-            cfgParseOptionKeyIdxName(optionId, optionKeyIdx));
+            cfgOptionIdxName(optionId, optionIdx));
     }
 
     FUNCTION_TEST_RETURN(UINT, result);
@@ -190,9 +190,9 @@ backupBlockIncrMap(void)
                 ManifestBlockIncrChecksumSizeMap manifestBuildBlockIncrChecksumSizeMap =
                 {
                     .blockSize = backupBlockIncrMapSize(
-                        cfgOptRepoBlockSizeMap, cfgOptionIdxDefault(cfgOptRepoBlockChecksumSizeMap), varStr(mapKey)),
+                        cfgOptRepoBlockChecksumSizeMap, cfgOptionIdxDefault(cfgOptRepoBlockChecksumSizeMap), varStr(mapKey)),
                     .checksumSize = backupBlockIncrMapChecksumSize(
-                        cfgOptRepoBlockSizeMap, cfgOptionIdxDefault(cfgOptRepoBlockChecksumSizeMap),
+                        cfgOptRepoBlockChecksumSizeMap, cfgOptionIdxDefault(cfgOptRepoBlockChecksumSizeMap),
                         kvGet(manifestBlockIncrChecksumSizeKv, mapKey)),
                 };
 
diff --git a/test/src/module/command/backupTest.c b/test/src/module/command/backupTest.c
index 6e77c6caa..3bec7d9b8 100644
--- a/test/src/module/command/backupTest.c
+++ b/test/src/module/command/backupTest.c
@@ -1090,21 +1090,38 @@ testRun(void)
     {
         TEST_TITLE("block incremental config map");
 
+        // Configure repo2 rather than repo1 so the index in the option name must come from the repo key
+        StringList *argList = strLstNew();
+        hrnCfgArgRawZ(argList, cfgOptStanza, "test1");
+        hrnCfgArgKeyRawZ(argList, cfgOptRepoPath, 2, TEST_PATH "/repo");
+        hrnCfgArgKeyRawZ(argList, cfgOptRepoRetentionFull, 2, "1");
+        hrnCfgArgRawZ(argList, cfgOptPgPath, TEST_PATH "/pg1");
+        HRN_CFG_LOAD(cfgCmdBackup, argList);
+
         TEST_ERROR(
             backupBlockIncrMapSize(cfgOptRepoBlockSizeMap, 0, STRDEF("0")), OptionInvalidValueError,
-            "'0' is not valid for 'repo1-block-size-map' option");
+            "'0' is not valid for 'repo2-block-size-map' option");
         TEST_ERROR(
             backupBlockIncrMapSize(cfgOptRepoBlockSizeMap, 0, STRDEF("Z")), OptionInvalidValueError,
-            "'Z' is not valid for 'repo1-block-size-map' option");
+            "'Z' is not valid for 'repo2-block-size-map' option");
         TEST_ERROR(
             backupBlockIncrMapSize(cfgOptRepoBlockSizeMap, 0, STRDEF("5GiB")), OptionInvalidValueError,
-            "'5GiB' is not valid for 'repo1-block-size-map' option");
+            "'5GiB' is not valid for 'repo2-block-size-map' option");
         TEST_ERROR(
             backupBlockIncrMapChecksumSize(cfgOptRepoBlockChecksumSizeMap, 0, VARSTRDEF("Z")), OptionInvalidValueError,
-            "'Z' is not valid for 'repo1-block-checksum-size-map' option");
+            "'Z' is not valid for 'repo2-block-checksum-size-map' option");
         TEST_ERROR(
             backupBlockIncrMapChecksumSize(cfgOptRepoBlockChecksumSizeMap, 0, VARSTRDEF("5")), OptionInvalidValueError,
-            "'5' is not valid for 'repo1-block-checksum-size-map' option");
+            "'5' is not valid for 'repo2-block-checksum-size-map' option");
+
+        // A key of the checksum size map is reported against the checksum size map rather than the size map
+        hrnCfgArgKeyRawBool(argList, cfgOptRepoBundle, 2, true);
+        hrnCfgArgKeyRawBool(argList, cfgOptRepoBlock, 2, true);
+        hrnCfgArgKeyRawZ(argList, cfgOptRepoBlockChecksumSizeMap, 2, "Z=16");
+        HRN_CFG_LOAD(cfgCmdBackup, argList);
+
+        TEST_ERROR(
+            backupBlockIncrMap(), OptionInvalidValueError, "'Z' is not valid for 'repo2-block-checksum-size-map' option");
 
         // -------------------------------------------------------------------------------------------------------------------------
         TEST_TITLE("full backup with zero block");