diff --git a/src/crystal/system/dir.cr b/src/crystal/system/dir.cr
index c5f57a04b82e..33d983c8e411 100644
--- a/src/crystal/system/dir.cr
+++ b/src/crystal/system/dir.cr
@@ -7,13 +7,14 @@ module Crystal::System::Dir
   # In particular we only care about the name and whether its
   # a directory or not to improve the performance of Dir.glob
   # by avoid having to call File.info on every directory entry.
+  # If dir is nil, the type is unknown.
   # In the future we might change Dir's API to expose these entries
   # with more info but right now it's not necessary.
   struct Entry
     getter name
     getter? dir
 
-    def initialize(@name : String, @dir : Bool)
+    def initialize(@name : String, @dir : Bool?)
     end
   end
 
diff --git a/src/crystal/system/unix/dir.cr b/src/crystal/system/unix/dir.cr
index 843595ad7dcd..75d1b18fdb5a 100644
--- a/src/crystal/system/unix/dir.cr
+++ b/src/crystal/system/unix/dir.cr
@@ -13,7 +13,12 @@ module Crystal::System::Dir
     Errno.value = Errno::NONE
     if entry = LibC.readdir(dir)
       name = String.new(entry.value.d_name.to_unsafe)
-      dir = entry.value.d_type == LibC::DT_DIR
+
+      dir = case entry.value.d_type
+            when LibC::DT_DIR     then true
+            when LibC::DT_UNKNOWN then nil
+            else                       false
+            end
       Entry.new(name, dir)
     elsif Errno.value != Errno::NONE
       raise ::File::Error.from_errno("Error reading directory entries", file: path)
diff --git a/src/dir/glob.cr b/src/dir/glob.cr
index 05a4601057ae..99b648f6747a 100644
--- a/src/dir/glob.cr
+++ b/src/dir/glob.cr
@@ -171,10 +171,10 @@ class Dir
             fullpath = Path[path].join("").to_s
           end
 
-          if dir_entry
-            yield fullpath if dir_entry.dir?
-          else
-            yield fullpath if dir?(fullpath)
+          if dir_entry && !dir_entry.dir?.nil?
+            yield fullpath
+          elsif dir?(fullpath)
+            yield fullpath
           end
         in EntryMatch
           return if sequence[pos + 1]?.is_a?(RecursiveDirectories)
@@ -187,8 +187,12 @@ class Dir
 
           each_child(path) do |entry|
             if cmd.matches?(entry.name)
-              if entry.dir?
-                fullpath = join(path, entry.name)
+              is_dir = entry.dir?
+              fullpath = join(path, entry.name)
+              if is_dir.nil?
+                is_dir = dir?(fullpath)
+              end
+              if is_dir
                 path_stack << {next_pos, fullpath, entry}
               end
             end
@@ -248,7 +252,12 @@ class Dir
                 yield fullpath if next_cmd.matches?(entry.name)
               end
 
-              if entry.dir?
+              is_dir = entry.dir?
+              if is_dir.nil?
+                is_dir = dir?(fullpath)
+              end
+
+              if is_dir
                 path_stack << {next_pos, fullpath, entry}
 
                 dir_path_stack.push fullpath
diff --git a/src/lib_c/aarch64-linux-gnu/c/dirent.cr b/src/lib_c/aarch64-linux-gnu/c/dirent.cr
index 3cb61b21129e..a6853d646279 100644
--- a/src/lib_c/aarch64-linux-gnu/c/dirent.cr
+++ b/src/lib_c/aarch64-linux-gnu/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_ino : InoT
diff --git a/src/lib_c/aarch64-linux-musl/c/dirent.cr b/src/lib_c/aarch64-linux-musl/c/dirent.cr
index c22a0a18666f..55662ab60f0e 100644
--- a/src/lib_c/aarch64-linux-musl/c/dirent.cr
+++ b/src/lib_c/aarch64-linux-musl/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_ino : InoT
diff --git a/src/lib_c/arm-linux-gnueabihf/c/dirent.cr b/src/lib_c/arm-linux-gnueabihf/c/dirent.cr
index 3cb61b21129e..a6853d646279 100644
--- a/src/lib_c/arm-linux-gnueabihf/c/dirent.cr
+++ b/src/lib_c/arm-linux-gnueabihf/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_ino : InoT
diff --git a/src/lib_c/i386-linux-gnu/c/dirent.cr b/src/lib_c/i386-linux-gnu/c/dirent.cr
index e4674e3bf0f4..714ccef24a19 100644
--- a/src/lib_c/i386-linux-gnu/c/dirent.cr
+++ b/src/lib_c/i386-linux-gnu/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_ino : InoT
diff --git a/src/lib_c/i386-linux-musl/c/dirent.cr b/src/lib_c/i386-linux-musl/c/dirent.cr
index c22a0a18666f..55662ab60f0e 100644
--- a/src/lib_c/i386-linux-musl/c/dirent.cr
+++ b/src/lib_c/i386-linux-musl/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_ino : InoT
diff --git a/src/lib_c/x86_64-darwin/c/dirent.cr b/src/lib_c/x86_64-darwin/c/dirent.cr
index 309689fa24f7..13f936e1042d 100644
--- a/src/lib_c/x86_64-darwin/c/dirent.cr
+++ b/src/lib_c/x86_64-darwin/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_ino : InoT
diff --git a/src/lib_c/x86_64-dragonfly/c/dirent.cr b/src/lib_c/x86_64-dragonfly/c/dirent.cr
index 51986d65e21c..044330a63b5d 100644
--- a/src/lib_c/x86_64-dragonfly/c/dirent.cr
+++ b/src/lib_c/x86_64-dragonfly/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_fileno : InoT
diff --git a/src/lib_c/x86_64-freebsd/c/dirent.cr b/src/lib_c/x86_64-freebsd/c/dirent.cr
index 0028289a3ced..bdad9169929f 100644
--- a/src/lib_c/x86_64-freebsd/c/dirent.cr
+++ b/src/lib_c/x86_64-freebsd/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     {% if flag?(:freebsd11) %}
diff --git a/src/lib_c/x86_64-linux-gnu/c/dirent.cr b/src/lib_c/x86_64-linux-gnu/c/dirent.cr
index 3cb61b21129e..a6853d646279 100644
--- a/src/lib_c/x86_64-linux-gnu/c/dirent.cr
+++ b/src/lib_c/x86_64-linux-gnu/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_ino : InoT
diff --git a/src/lib_c/x86_64-linux-musl/c/dirent.cr b/src/lib_c/x86_64-linux-musl/c/dirent.cr
index c22a0a18666f..55662ab60f0e 100644
--- a/src/lib_c/x86_64-linux-musl/c/dirent.cr
+++ b/src/lib_c/x86_64-linux-musl/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_ino : InoT
diff --git a/src/lib_c/x86_64-netbsd/c/dirent.cr b/src/lib_c/x86_64-netbsd/c/dirent.cr
index 4b3186ab6a97..78197bbc29c6 100644
--- a/src/lib_c/x86_64-netbsd/c/dirent.cr
+++ b/src/lib_c/x86_64-netbsd/c/dirent.cr
@@ -13,7 +13,8 @@ lib LibC
     dd_lock : Void*
   end
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_fileno : InoT
diff --git a/src/lib_c/x86_64-openbsd/c/dirent.cr b/src/lib_c/x86_64-openbsd/c/dirent.cr
index 125d64740e38..e332bd30c8f6 100644
--- a/src/lib_c/x86_64-openbsd/c/dirent.cr
+++ b/src/lib_c/x86_64-openbsd/c/dirent.cr
@@ -3,7 +3,8 @@ require "./sys/types"
 lib LibC
   type DIR = Void
 
-  DT_DIR = 4
+  DT_UNKNOWN = 0
+  DT_DIR     = 4
 
   struct Dirent
     d_fileno : InoT