diff --git a/src/Psalm/Config.php b/src/Psalm/Config.php
index 006fdad57..82d975670 100644
--- a/src/Psalm/Config.php
+++ b/src/Psalm/Config.php
@@ -1924,9 +1924,6 @@ class Config
             throw new LogicException("IncludeCollector should be set at this point");
         }
 
-        $this->collectPredefinedConstants();
-        $this->collectPredefinedFunctions();
-
         $vendor_autoload_files_path
             = $this->base_dir . DIRECTORY_SEPARATOR . 'vendor'
                 . DIRECTORY_SEPARATOR . 'composer' . DIRECTORY_SEPARATOR . 'autoload_files.php';
@@ -1945,6 +1942,8 @@ class Config
 
         $codebase = $project_analyzer->getCodebase();
 
+        $this->collectPredefinedFunctions();
+
         if ($this->autoloader) {
             // somee classes that we think are missing may not actually be missing
             // as they might be autoloadable once we require the autoloader below
@@ -1959,6 +1958,8 @@ class Config
             );
         }
 
+        $this->collectPredefinedConstants();
+
         $autoload_included_files = $this->include_collector->getFilteredIncludedFiles();
 
         if ($autoload_included_files) {
diff --git a/src/Psalm/Internal/PhpVisitor/ReflectorVisitor.php b/src/Psalm/Internal/PhpVisitor/ReflectorVisitor.php
index e78d66c48..c6c97ed85 100644
--- a/src/Psalm/Internal/PhpVisitor/ReflectorVisitor.php
+++ b/src/Psalm/Internal/PhpVisitor/ReflectorVisitor.php
@@ -860,7 +860,9 @@ class ReflectorVisitor extends PhpParser\NodeVisitorAbstract implements PhpParse
                         $this->file_storage->declaring_constants[$const_name] = $this->file_path;
                     }
 
-                    if ($this->codebase->register_stub_files || $this->codebase->register_autoload_files) {
+                    if (($this->codebase->register_stub_files || $this->codebase->register_autoload_files)
+                        && !\defined($const_name)
+                    ) {
                         $this->codebase->addGlobalConstantType($const_name, $const_type);
                     }
                 }
diff --git a/tests/StubTest.php b/tests/StubTest.php
index af24010da..f082a1f81 100644
--- a/tests/StubTest.php
+++ b/tests/StubTest.php
@@ -509,6 +509,7 @@ class StubTest extends TestCase
                 dirname(__DIR__),
                 '<?xml version="1.0"?>
                 <psalm
+                    errorLevel="1"
                     autoloader="tests/fixtures/stubs/polyfill.php"
                 >
                     <projectFiles>
@@ -530,6 +531,37 @@ class StubTest extends TestCase
         $this->analyzeFile($file_path, new Context());
     }
 
+    /**
+     * @return void
+     */
+    public function testConditionalConstantDefined()
+    {
+        $this->project_analyzer = $this->getProjectAnalyzerWithConfig(
+            TestConfig::loadFromXML(
+                dirname(__DIR__),
+                '<?xml version="1.0"?>
+                <psalm
+                    errorLevel="1"
+                    autoloader="tests/fixtures/stubs/conditional_constant_define_inferred.php"
+                >
+                    <projectFiles>
+                        <directory name="src" />
+                    </projectFiles>
+                </psalm>'
+            )
+        );
+
+        $file_path = getcwd() . '/src/somefile.php';
+
+        $this->addFile(
+            $file_path,
+            '<?php
+                echo CODE_DIR;'
+        );
+
+        $this->analyzeFile($file_path, new Context());
+    }
+
     /**
      * @return void
      */
@@ -540,6 +572,7 @@ class StubTest extends TestCase
                 dirname(__DIR__),
                 '<?xml version="1.0"?>
                 <psalm
+                    errorLevel="1"
                     autoloader="tests/fixtures/stubs/class_alias.php"
                 >
                     <projectFiles>
diff --git a/tests/fixtures/stubs/conditional_constant_define_inferred.php b/tests/fixtures/stubs/conditional_constant_define_inferred.php
new file mode 100644
index 000000000..af6d3d6ab
--- /dev/null
+++ b/tests/fixtures/stubs/conditional_constant_define_inferred.php
@@ -0,0 +1,6 @@
+<?php
+
+if (!defined('CODE_DIR')) {
+   $codeDir = 1;
+   define('CODE_DIR', $codeDir);
+}