diff --git a/Makefile b/Makefile
index d5a7137..4a33b99 100644
--- a/Makefile
+++ b/Makefile
@@ -26,7 +26,7 @@ SUBDIR_LIB := libslunkcrypt
 # ---------------------------------------------------------------------------
 
 CONFIG =
-LDFLGS = -lpthread
+LDFLGS =
 CFLAGS = -I$(SUBDIR_LIB)/include -std=gnu99 -Wall -pedantic
 
 ifneq (,$(firstword $(filter 32 64,$(CPU))))
@@ -76,20 +76,22 @@ else
   SUFFIX :=
 endif
 
-ifeq ($(THREAD),0)
-  CFLAGS += -DSLUNKBUILD_NOTHREADS
-endif
-
-ifneq ($(STRIP),0)
-  LDFLGS += -s
+ifneq (,$(firstword $(filter %-w64-mingw32 %w64-windows-gnu,$(MACHINE))))
+  LDFLGS += -mconsole -municode
 endif
 
 ifeq ($(STATIC),1)
   LDFLGS += -static
 endif
 
-ifneq (,$(firstword $(filter %-w64-mingw32 %w64-windows-gnu,$(MACHINE))))
-  LDFLGS += -mconsole -municode
+ifneq ($(STRIP),0)
+  LDFLGS += -s
+endif
+
+ifeq ($(THREAD),1)
+  LDFLGS += -lpthread
+else
+  CFLAGS += -DSLUNKBUILD_NOTHREADS
 endif
 
 ifneq (,$(firstword $(filter %-unknown-haiku,$(MACHINE))))
diff --git a/libslunkcrypt/src/junk.c b/libslunkcrypt/src/junk.c
index 70064ee..c70586c 100644
--- a/libslunkcrypt/src/junk.c
+++ b/libslunkcrypt/src/junk.c
@@ -19,12 +19,6 @@
 #include <fcntl.h>
 #include <limits.h>
 
-/* PThread */
-#if defined(_MSC_VER) && !defined(_DLL)
-#  define PTW32_STATIC_LIB 1
-#endif
-#include <pthread.h>
-
 /* Utils */
 static INLINE size_t MIN_SIZE(const size_t a, const size_t b) { return (a > b) ? b : a; }
 
@@ -37,7 +31,6 @@ static INLINE size_t MIN_SIZE(const size_t a, const size_t b) { return (a > b) ?
 #  include <io.h>
 #else
 #  include <unistd.h>
-#  include <pthread.h>
 #endif
 
 /* detect compiler destructor support */
@@ -67,6 +60,34 @@ static INLINE size_t MIN_SIZE(const size_t a, const size_t b) { return (a > b) ?
 #  pragma message("Function explicit_bzero() is *not* available -> using fallback!")
 #endif
 
+// ==========================================================================
+// One-time initialization
+// ==========================================================================
+
+/* atomic memory access */
+#if defined(_WIN32)
+#  define ATOMIC_EXCHANGE(X,Y) InterlockedExchange((X),(Y))
+#  define ATOMIC_COMPARE_EXCHANGE(X,Y,Z) InterlockedCompareExchange((X),(Y),(Z))
+#else
+#  define ATOMIC_EXCHANGE(X,Y) __sync_lock_test_and_set((X),(Y))
+#  define ATOMIC_COMPARE_EXCHANGE(X,Y,Z) __sync_val_compare_and_swap((X),(Z),(Y))
+#endif
+
+/* execute initialization function once */
+static void initialize_once(volatile long *const once_flag, void (*const init_routine)(void))
+{
+	long state;
+	while ((state = ATOMIC_COMPARE_EXCHANGE(once_flag, -1, 0)) != 0)
+	{
+		if (state > 0)
+		{
+			return; /*already initialized*/
+		}
+	}
+	init_routine();
+	ATOMIC_EXCHANGE(once_flag, 1);
+}
+
 // ==========================================================================
 // Random bytes
 // ==========================================================================
@@ -74,7 +95,7 @@ static INLINE size_t MIN_SIZE(const size_t a, const size_t b) { return (a > b) ?
 #define MAX_COUNT 1048576U
 
 /* Global state */
-static pthread_once_t s_random_is_initialized = PTHREAD_ONCE_INIT;
+static volatile long s_random_is_initialized = 0L;
 #if defined(_WIN32)
 typedef BOOLEAN(WINAPI *ptr_genrandom_t)(void *buffer, ULONG length);
 static HMODULE s_advapi32 = NULL;
@@ -140,7 +161,7 @@ init_completed: ;
 size_t slunkcrypt_random_bytes(uint8_t *const buffer, const size_t length)
 {
 	size_t offset;
-	pthread_once(&s_random_is_initialized, init_random_source);
+	initialize_once(&s_random_is_initialized, init_random_source);
 #ifdef HAVE_WIN32RTLGENRANDOM
 	if (s_genrandom)
 	{