diff --git a/Sources/Prometheus/NIOLock.swift b/Sources/Prometheus/NIOLock.swift
index 69bb58f..3064360 100644
--- a/Sources/Prometheus/NIOLock.swift
+++ b/Sources/Prometheus/NIOLock.swift
@@ -48,6 +48,9 @@ import wasi_pthread
 #if os(Windows)
 @usableFromInline
 typealias LockPrimitive = SRWLOCK
+#elseif os(FreeBSD) || os(OpenBSD)
+@usableFromInline
+typealias LockPrimitive = pthread_mutex_t?
 #else
 @usableFromInline
 typealias LockPrimitive = pthread_mutex_t
@@ -64,11 +67,19 @@ extension LockOperations {
         #if os(Windows)
         InitializeSRWLock(mutex)
         #elseif (compiler(<6.1) && !os(WASI)) || (compiler(>=6.1) && _runtime(_multithreaded))
+        #if os(FreeBSD) || os(OpenBSD)
+        var attr = pthread_mutexattr_t(bitPattern: 0)
+        #else
         var attr = pthread_mutexattr_t()
+        #endif
         pthread_mutexattr_init(&attr)
         assert(
             {
+                #if os(FreeBSD) || os(OpenBSD)
+                pthread_mutexattr_settype(&attr, .init(PTHREAD_MUTEX_ERRORCHECK.rawValue))
+                #else
                 pthread_mutexattr_settype(&attr, .init(PTHREAD_MUTEX_ERRORCHECK))
+                #endif
                 return true
             }()
         )