diff --git a/bin/gen_base_callmap.php b/bin/gen_base_callmap.php
index 0efd6ae0693..9ccd930839a 100644
--- a/bin/gen_base_callmap.php
+++ b/bin/gen_base_callmap.php
@@ -62,7 +62,7 @@ function paramsToEntries(ReflectionFunctionAbstract $reflectionFunction): array
 
     $args = paramsToEntries($func);
 
-    $callmap[$name] = $args;
+    $callmap[strtolower($name)] = $args;
 }
 
 foreach (get_declared_classes() as $class) {
@@ -74,7 +74,7 @@ function paramsToEntries(ReflectionFunctionAbstract $reflectionFunction): array
     foreach ($refl->getMethods() as $method) {
         $args = paramsToEntries($method);
     
-        $callmap[$class.'::'.$method->getName()] = $args;
+        $callmap[strtolower($class.'::'.$method->getName())] = $args;
     }
 }
 
diff --git a/bin/gen_callmap.php b/bin/gen_callmap.php
index 22dadb5e9b4..a7e15ff8900 100644
--- a/bin/gen_callmap.php
+++ b/bin/gen_callmap.php
@@ -2,10 +2,11 @@
 
 declare(strict_types=1);
 
-// Written by SamMousa in https://github.com/vimeo/psalm/issues/8101, finalized by @danog
-
 require __DIR__ . '/gen_callmap_utils.php';
 
+$callMap = require "dictionaries/CallMap.php";
+$orig = $callMap;
+
 foreach ($callMap as $functionName => &$entry) {
     $refl = getReflectionFunction($functionName);
     if (!$refl) {
diff --git a/bin/gen_callmap_utils.php b/bin/gen_callmap_utils.php
index b244ce57155..983f470701e 100644
--- a/bin/gen_callmap_utils.php
+++ b/bin/gen_callmap_utils.php
@@ -199,7 +199,5 @@ function writeCallMap(string $file, array $callMap): void
 BypassFinals::enable();
 
 new ProjectAnalyzer(new TestConfig, new Providers(new FileProvider));
-$callMap = require "dictionaries/CallMap.php";
-$orig = $callMap;
 
 $codebase = ProjectAnalyzer::getInstance()->getCodebase();
diff --git a/bin/normalize-callmap.php b/bin/normalize-callmap.php
index 00a201c824f..f3dee84a59a 100644
--- a/bin/normalize-callmap.php
+++ b/bin/normalize-callmap.php
@@ -2,10 +2,63 @@
 
 declare(strict_types=1);
 
+use Webmozart\Assert\Assert;
+
 require __DIR__ . '/gen_callmap_utils.php';
 
-foreach (glob(__DIR__."/../dictionaries/CallMap*.php") as $file) {
-    $callMap = require $file;
-    $callMap = normalizeCallMap($callMap);
-    writeCallMap($file, $callMap);
+$baseMaps = [];
+
+foreach (glob(__DIR__."/../dictionaries/base/CallMap_*.php") as $file) {
+    Assert::eq(preg_match('/_(\d+)\.php/', $file, $matches), 1);
+    $version = $matches[1];
+
+    $baseMaps[$version] = normalizeCallMap(require $file);
+}
+
+ksort($baseMaps);
+$last = array_key_last($baseMaps);
+
+$customMaps = [
+    $last => normalizeCallMap(require __DIR__."/../dictionaries/override/CallMap.php")
+];
+
+$diffs = [];
+foreach (glob(__DIR__."/../dictionaries/override/CallMap_*.php") as $file) {
+    Assert::eq(preg_match('/_(\d+)_delta\.php/', $file, $matches), 1);
+    $version = $matches[1];
+    $diffs[$version] = normalizeCallMap(require $file);
 }
+krsort($diffs);
+
+$versions = array_reverse(array_keys($diffs));
+
+foreach ($diffs as $version => $diff) {
+    $callMap = $customMaps[$version];
+    $diff = normalizeCallMap(require $file);
+    foreach ($diff['removed'] as $func => $descr) {
+        $callMap[$func] = $descr;
+    }
+    foreach ($diff['added'] as $func => $descr) {
+        unset($callMap[$func]);
+    }
+    foreach ($diff['changed'] as $func => $sub) {
+        $callMap[$func] = $sub['old'];
+    }
+
+    $prevVersion = array_search($version, $versions)-1;
+    if ($prevVersion < 0) {
+        continue;
+    }
+    $customMaps[$versions[$prevVersion]] = $callMap;
+}
+
+foreach ($customMaps as $version => $data) {
+    foreach ($data as $name => $func) {
+        if (($baseMaps[$version][$name] ?? null) === $func) {
+            unset($customMaps[$version][$name]);
+        } else if(($baseMaps[$version][$name] ?? null))
+        var_dump($name, ($baseMaps[$version][$name] ?? null), $func);
+    }
+}
+
+var_dump($customMaps);
\ No newline at end of file