diff --git a/bearssl.nimble b/bearssl.nimble
index b37522e..c5d4659 100644
--- a/bearssl.nimble
+++ b/bearssl.nimble
@@ -8,7 +8,7 @@ license       = "MIT or Apache License 2.0"
 skipDirs      = @["tests"]
 
 requires "nim >= 1.6.0",
-         "unittest2"
+         "unittest2 >= 0.0.5 & <= 0.1.0"
 
 let nimc = getEnv("NIMC", "nim") # Which nim compiler to use
 let lang = getEnv("NIMLANG", "c") # Which backend (c/cpp/js)