diff --git a/.github/workflows/os-check.yml b/.github/workflows/os-check.yml
index 4baea6b830..38f7488f6b 100644
--- a/.github/workflows/os-check.yml
+++ b/.github/workflows/os-check.yml
@@ -98,6 +98,7 @@ jobs:
           '--enable-curve25519=nonblock --enable-ecc=nonblock --enable-sp=yes,nonblock CPPFLAGS="-DWOLFSSL_PUBLIC_MP -DWOLFSSL_DEBUG_NONBLOCK"',
           '--enable-certreq --enable-certext --enable-certgen --disable-secure-renegotiation-info CPPFLAGS="-DNO_TLS"',
           '--enable-ocsp --enable-ocsp-responder --enable-ocspstapling CPPFLAGS="-DWOLFSSL_NONBLOCK_OCSP" --enable-maxfragment',
+          '--enable-all CPPFLAGS=-DWOLFSSL_HASH_KEEP',
         ]
     name: make check
     if: github.repository_owner == 'wolfssl'
diff --git a/wolfcrypt/src/hash.c b/wolfcrypt/src/hash.c
index 61f7aacd63..64a6308c91 100644
--- a/wolfcrypt/src/hash.c
+++ b/wolfcrypt/src/hash.c
@@ -1956,9 +1956,14 @@ int _wc_Hash_Grow(byte** msg, word32* used, word32* len, const byte* in,
 {
     word32 usedSz = 0;
 
-    if (inSz <= 0 || !WC_SAFE_SUM_WORD32(*used, (word32)inSz, usedSz))
+    if (inSz < 0 || !WC_SAFE_SUM_WORD32(*used, (word32)inSz, usedSz))
         return BAD_FUNC_ARG;
 
+    /* Allow zero-length input as a no-op. Some callers may pass zero-length
+     * data during hash operations and this should not be treated as an error. */
+    if (inSz == 0)
+        return 0;
+
     if (*len < usedSz) {
         if (*msg == NULL) {
             *msg = (byte*)XMALLOC(usedSz, heap, DYNAMIC_TYPE_TMP_BUFFER);
diff --git a/wolfcrypt/src/port/maxim/max3266x.c b/wolfcrypt/src/port/maxim/max3266x.c
index c05c2781b0..4aed830c00 100644
--- a/wolfcrypt/src/port/maxim/max3266x.c
+++ b/wolfcrypt/src/port/maxim/max3266x.c
@@ -808,23 +808,26 @@ int wc_MXC_TPU_SHA_Copy(void* src, void* dst, word32 ctxSz,
                                 byte** dstMsg, word32* dstUsed, word32* dstLen,
                                 void* dstHeap, void* srcHeap)
 {
-    byte* srcBuf;
+    byte* srcBuf = NULL;
 
     if (src == NULL || dst == NULL || dstMsg == NULL ||
         dstUsed == NULL || dstLen == NULL || ctxSz == 0) {
         return BAD_FUNC_ARG;
     }
 
-    srcBuf = *dstMsg;
-
     /* Free existing dst msg buffer using dst's original heap */
     wc_MXC_TPU_SHA_Free(dstMsg, dstUsed, dstLen, dstHeap);
 
     /* Shallow copy the full context struct */
     XMEMCPY(dst, src, ctxSz);
 
-    /* Deep copy src msg buffer if present, allocate using src's heap */
-    if (srcBuf != NULL) {
+    /* Deep copy src msg buffer if present. Since dstMsg points into the dst
+     * struct, the XMEMCPY above overwrites it with the src's msg pointer.
+     * Save that pointer, allocate a new buffer for dst, and copy the data.
+     * Do NOT move srcBuf assignment before XMEMCPY - it must capture the
+     * src msg pointer that lands in *dstMsg after the shallow copy. */
+    if (*dstMsg != NULL) {
+        srcBuf = *dstMsg;
         *dstMsg = (byte*)XMALLOC(*dstLen, srcHeap, DYNAMIC_TYPE_TMP_BUFFER);
         if (*dstMsg == NULL) {
             return MEMORY_E;