diff --git a/CMakeLists.txt b/CMakeLists.txt
index 46ef593d..e5d9b6b7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -30,7 +30,7 @@ if(MEMSAN)
   set(CMAKE_ARGS_MEMCHECK_LIB "-stdlib=libc++ -L${LLVM_PRJ_LIB} -lc++abi -Wl,-rpath,${LLVM_PRJ_LIB}")
   set(CMAKE_ARGS_MEMCHECK_INC "-isystem -I${LLVM_PRJ_INC} -I${LLVM_PRJ_INC}/c++/v1")
   set(CMAKE_ARGS_MEMCHECK_FLAGS "-fsanitize=memory -fsanitize-memory-track-origins=2 -fno-omit-frame-pointer -Wno-unused-command-line-argument")
-  set(EXTRA_CXX_FLAGS "${CMAKE_ARGS_MEMCHECK_FLAGS} ${CMAKE_ARGS_MEMCHECK_LIB} ${CMAKE_ARGS_MEMCHECK_INC}")
+  set(EXTRA_CXX_FLAGS "${CMAKE_ARGS_MEMCHECK_FLAGS} ${CMAKE_ARGS_MEMCHECK_LIB} ${CMAKE_ARGS_MEMCHECK_INC} -DPQC_MEMSAN_BUILD")
 endif()
 
 # Dependencies
diff --git a/src/common/randombytes.c b/src/common/randombytes.c
index f2896ea6..b0096333 100644
--- a/src/common/randombytes.c
+++ b/src/common/randombytes.c
@@ -301,6 +301,10 @@ static int randombytes_js_randombytes_nodejs(void *buf, size_t n) {
 #endif /* defined(__EMSCRIPTEN__) */
 
 int randombytes(uint8_t *buf, size_t n) {
+#ifdef PQC_MEMSAN_BUILD
+    size_t i;
+    for (i=0; i<n; i++) buf[i]=0;
+#endif
     #if defined(__EMSCRIPTEN__)
     return randombytes_js_randombytes_nodejs(buf, n);
     #elif defined(__linux__)
diff --git a/src/kem/sike/p434/sike.c b/src/kem/sike/p434/sike.c
index 27ea1e4b..5963ac5e 100644
--- a/src/kem/sike/p434/sike.c
+++ b/src/kem/sike/p434/sike.c
@@ -103,7 +103,7 @@ static inline void sike_init_basis(const crypto_word_t *gen, f2elm_t XP, f2elm_t
 
 // Conversion of GF(p^2) element from Montgomery to standard representation.
 static inline void sike_fp2_encode(const f2elm_t x, uint8_t *enc) {
-    f2elm_t t;
+    f2elm_t t={0};
     sike_from_fp2mont(x, t);
 
     // convert to bytes in little endian form
diff --git a/test/bench/kyber.cc b/test/bench/kyber.cc
index 07fdd762..97676bf5 100644
--- a/test/bench/kyber.cc
+++ b/test/bench/kyber.cc
@@ -22,7 +22,7 @@ auto cpucycle = [](benchmark::State &st, int64_t cycles) {
 static void BenchKyberMatK2(benchmark::State &st) {
 	int64_t t, total = 0;
 	polyvec a[KYBER_K];
-	uint8_t seed[32];
+	uint8_t seed[32] = {0};
     for (auto _ : st) {
         t = benchmark::cycleclock::Now();
         PQCLEAN_KYBER512_AVX2_gen_matrix(a, seed, 0);
diff --git a/test/ut.cpp b/test/ut.cpp
index 5e58a5e6..5b902bb4 100644
--- a/test/ut.cpp
+++ b/test/ut.cpp
@@ -2,6 +2,7 @@
 #include <vector>
 #include <gtest/gtest.h>
 #include <pqc/pqc.h>
+#include <random>
 
 TEST(Kyber,KEMOneOff) {
 
@@ -27,10 +28,15 @@ TEST(Kyber,KEMOneOff) {
 
 TEST(Kyber,SIGNOneOff) {
 
+    std::random_device rd;
+    std::uniform_int_distribution<uint8_t> dist(0, 0xFF);
+    uint8_t msg[1234] = {0};
+
 	for (int i=0; i<PQC_ALG_SIG_MAX; i++) {
 		const pqc_ctx_t *p = pqc_sig_alg_by_id(i);
+		// generate some random msg
+		for (auto &x : msg) {x = dist(rd);}
 
-		uint8_t msg[1234];
 	    std::vector<uint8_t> sig(pqc_signature_bsz(p));
 	    std::vector<uint8_t> sk(pqc_private_key_bsz(p));
 	    std::vector<uint8_t> pk(pqc_public_key_bsz(p));