diff --git a/test/app/digest.result b/test/app/digest.result
index bf1815136753a8a603ed1c47c6a1afc3b33f3636..d41efde3fa99c05d10aee70f70b92fd1fb4b7c45 100644
--- a/test/app/digest.result
+++ b/test/app/digest.result
@@ -5,6 +5,9 @@ test_run:cmd("push filter ".."'\\.lua.*:[0-9]+: ' to '.lua:<line>\"]: '")
 ---
 - true
 ...
+fiber = require('fiber')
+---
+...
 digest = require('digest')
 ---
 ...
@@ -576,3 +579,60 @@ test_run:cmd("clear filter")
 ---
 - true
 ...
+-- gh-3396: fiber-safe pbkdf2
+res = {}
+---
+...
+sentry = fiber.channel()
+---
+...
+_ = test_run:cmd("setopt delimiter ';'")
+---
+...
+function test_pbkdf2()
+    local digest = require('digest')
+    for i = 1, 10 do
+        table.insert(res, digest.pbkdf2('', 'salt', 100, 32):hex())
+    end
+    sentry:put(fiber.id())
+end;
+---
+...
+_ = test_run:cmd("setopt delimiter ''");
+---
+...
+_ = fiber.create(test_pbkdf2)
+---
+...
+_ = fiber.create(test_pbkdf2)
+---
+...
+_ = sentry:get()
+---
+...
+_ = sentry:get()
+---
+...
+res
+---
+- - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+  - bafac115a0022b2894f2983b5b5102455bdd3ba7cfbeb09f219a9fde8f3ee6a9
+...
diff --git a/test/app/digest.test.lua b/test/app/digest.test.lua
index 3134efc92caa0a546a28f7d47869a263e86883a5..7ecda91bcbf95beac5a78681abec8a53819c04ff 100644
--- a/test/app/digest.test.lua
+++ b/test/app/digest.test.lua
@@ -1,6 +1,7 @@
 test_run = require('test_run').new()
 test_run:cmd("push filter ".."'\\.lua.*:[0-9]+: ' to '.lua:<line>\"]: '")
 
+fiber = require('fiber')
 digest = require('digest')
 type(digest)
 
@@ -184,3 +185,21 @@ s
 err:match("number")
 digest = nil
 test_run:cmd("clear filter")
+
+-- gh-3396: fiber-safe pbkdf2
+res = {}
+sentry = fiber.channel()
+_ = test_run:cmd("setopt delimiter ';'")
+function test_pbkdf2()
+    local digest = require('digest')
+    for i = 1, 10 do
+        table.insert(res, digest.pbkdf2('', 'salt', 100, 32):hex())
+    end
+    sentry:put(fiber.id())
+end;
+_ = test_run:cmd("setopt delimiter ''");
+_ = fiber.create(test_pbkdf2)
+_ = fiber.create(test_pbkdf2)
+_ = sentry:get()
+_ = sentry:get()
+res