diff --git a/src/scalar_4x64_impl.h b/src/scalar_4x64_impl.h
index 7ef726f7..11622b0f 100644
--- a/src/scalar_4x64_impl.h
+++ b/src/scalar_4x64_impl.h
@@ -882,7 +882,7 @@ static void secp256k1_scalar_mul_512(uint64_t *l8, const secp256k1_scalar *a, co
 #endif
 }
 
-static void secp256k1_scalar_sqr_512(uint64_t l[8], const secp256k1_scalar *a) {
+static void secp256k1_scalar_sqr_512(uint64_t *l8, const secp256k1_scalar *a) {
 #ifdef USE_ASM_X86_64
     __asm__ __volatile__(
     /* Preload */
@@ -893,7 +893,7 @@ static void secp256k1_scalar_sqr_512(uint64_t l[8], const secp256k1_scalar *a) {
     /* (rax,rdx) = a0 * a0 */
     "movq %%r11, %%rax\n"
     "mulq %%r11\n"
-    /* Extract l0 */
+    /* Extract l8[0] */
     "movq %%rax, 0(%%rsi)\n"
     /* (r8,r9,r10) = (rdx,0) */
     "movq %%rdx, %%r8\n"
@@ -908,7 +908,7 @@ static void secp256k1_scalar_sqr_512(uint64_t l[8], const secp256k1_scalar *a) {
     "addq %%rax, %%r8\n"
     "adcq %%rdx, %%r9\n"
     "adcq $0, %%r10\n"
-    /* Extract l1 */
+    /* Extract l8[1] */
     "movq %%r8, 8(%%rsi)\n"
     "xorq %%r8, %%r8\n"
     /* (r9,r10,r8) += 2 * a0 * a2 */
@@ -926,7 +926,7 @@ static void secp256k1_scalar_sqr_512(uint64_t l[8], const secp256k1_scalar *a) {
     "addq %%rax, %%r9\n"
     "adcq %%rdx, %%r10\n"
     "adcq $0, %%r8\n"
-    /* Extract l2 */
+    /* Extract l8[2] */
     "movq %%r9, 16(%%rsi)\n"
     "xorq %%r9, %%r9\n"
     /* (r10,r8,r9) += 2 * a0 * a3 */
@@ -947,7 +947,7 @@ static void secp256k1_scalar_sqr_512(uint64_t l[8], const secp256k1_scalar *a) {
     "addq %%rax, %%r10\n"
     "adcq %%rdx, %%r8\n"
     "adcq $0, %%r9\n"
-    /* Extract l3 */
+    /* Extract l8[3] */
     "movq %%r10, 24(%%rsi)\n"
     "xorq %%r10, %%r10\n"
     /* (r8,r9,r10) += 2 * a1 * a3 */
@@ -965,7 +965,7 @@ static void secp256k1_scalar_sqr_512(uint64_t l[8], const secp256k1_scalar *a) {
     "addq %%rax, %%r8\n"
     "adcq %%rdx, %%r9\n"
     "adcq $0, %%r10\n"
-    /* Extract l4 */
+    /* Extract l8[4] */
     "movq %%r8, 32(%%rsi)\n"
     "xorq %%r8, %%r8\n"
     /* (r9,r10,r8) += 2 * a2 * a3 */
@@ -977,45 +977,48 @@ static void secp256k1_scalar_sqr_512(uint64_t l[8], const secp256k1_scalar *a) {
     "addq %%rax, %%r9\n"
     "adcq %%rdx, %%r10\n"
     "adcq $0, %%r8\n"
-    /* Extract l5 */
+    /* Extract l8[5] */
     "movq %%r9, 40(%%rsi)\n"
     /* (r10,r8) += a3 * a3 */
     "movq %%r14, %%rax\n"
     "mulq %%r14\n"
     "addq %%rax, %%r10\n"
     "adcq %%rdx, %%r8\n"
-    /* Extract l6 */
+    /* Extract l8[6] */
     "movq %%r10, 48(%%rsi)\n"
-    /* Extract l7 */
+    /* Extract l8[7] */
     "movq %%r8, 56(%%rsi)\n"
     :
-    : "S"(l), "D"(a->d)
+    : "S"(l8), "D"(a->d)
     : "rax", "rdx", "r8", "r9", "r10", "r11", "r12", "r13", "r14", "cc", "memory");
+
+    SECP256K1_CHECKMEM_MSAN_DEFINE(l8, sizeof(*l8) * 8);
+
 #else
     /* 160 bit accumulator. */
     uint64_t c0 = 0, c1 = 0;
     uint32_t c2 = 0;
 
-    /* l[0..7] = a[0..3] * b[0..3]. */
+    /* l8[0..7] = a[0..3] * b[0..3]. */
     muladd_fast(a->d[0], a->d[0]);
-    extract_fast(l[0]);
+    extract_fast(l8[0]);
     muladd2(a->d[0], a->d[1]);
-    extract(l[1]);
+    extract(l8[1]);
     muladd2(a->d[0], a->d[2]);
     muladd(a->d[1], a->d[1]);
-    extract(l[2]);
+    extract(l8[2]);
     muladd2(a->d[0], a->d[3]);
     muladd2(a->d[1], a->d[2]);
-    extract(l[3]);
+    extract(l8[3]);
     muladd2(a->d[1], a->d[3]);
     muladd(a->d[2], a->d[2]);
-    extract(l[4]);
+    extract(l8[4]);
     muladd2(a->d[2], a->d[3]);
-    extract(l[5]);
+    extract(l8[5]);
     muladd_fast(a->d[3], a->d[3]);
-    extract_fast(l[6]);
+    extract_fast(l8[6]);
     VERIFY_CHECK(c1 == 0);
-    l[7] = c0;
+    l8[7] = c0;
 #endif
 }