diff --git a/riscv/riscv_vector_opm_instructions.cc b/riscv/riscv_vector_opm_instructions.cc
index 234a01f..d286e5d 100644
--- a/riscv/riscv_vector_opm_instructions.cc
+++ b/riscv/riscv_vector_opm_instructions.cc
@@ -190,6 +190,14 @@
     RiscVVectorState* rv_vector, const Instruction* inst,
     std::function<uint8_t(uint8_t, uint8_t)> op) {
   if (rv_vector->vector_exception()) return;
+  int vstart = rv_vector->vstart();
+  int vlen = rv_vector->vector_length();
+
+  if (vstart >= vlen) {
+    rv_vector->clear_vstart();
+    return;
+  }
+
   // Get spans for vector source and destination registers.
   auto* vs2_op = static_cast<RV32VectorSourceOperand*>(inst->Source(0));
   auto vs2_span = vs2_op->GetRegister(0)->data_buffer()->Get<uint8_t>();
@@ -199,22 +207,35 @@
       static_cast<RV32VectorDestinationOperand*>(inst->Destination(0));
   auto* vd_db = vd_op->CopyDataBuffer();
   auto vd_span = vd_db->Get<uint8_t>();
-  // Compute start and end locations.
 
-  int vstart = rv_vector->vstart();
+  // Compute start and end locations.
   int start_byte = vstart / 8;
   int start_offset = vstart % 8;
+  uint8_t start_mask = 0b1111'1111 << start_offset;
 
-  if (start_byte < vd_span.size()) {
-    uint8_t start_mask = 0b1111'1111 << start_offset;
+  int end_byte = (vlen - 1) / 8;
+  int end_offset = (vlen - 1) % 8;
+  uint8_t end_mask = 0b1111'1111 >> (7 - end_offset);
+
+  if (start_byte == end_byte) {
+    uint8_t mask = start_mask & end_mask;
+    vd_span[start_byte] =
+        (op(vs2_span[start_byte], vs1_span[start_byte]) & mask) |
+        (vd_span[start_byte] & ~mask);
+  } else {
     vd_span[start_byte] =
         (op(vs2_span[start_byte], vs1_span[start_byte]) & start_mask) |
         (vd_span[start_byte] & ~start_mask);
+
+    for (int i = start_byte + 1; i < end_byte; i++) {
+      vd_span[i] = op(vs2_span[i], vs1_span[i]);
+    }
+
+    vd_span[end_byte] =
+        (op(vs2_span[end_byte], vs1_span[end_byte]) & end_mask) |
+        (vd_span[end_byte] & ~end_mask);
   }
 
-  for (int i = start_byte + 1; i < vd_span.size(); i++) {
-    vd_span[i] = op(vs2_span[i], vs1_span[i]);
-  }
   vd_db->Submit();
   rv_vector->clear_vstart();
 }
diff --git a/riscv/riscv_vector_unary_instructions.cc b/riscv/riscv_vector_unary_instructions.cc
index 6769b71..7ab4687 100644
--- a/riscv/riscv_vector_unary_instructions.cc
+++ b/riscv/riscv_vector_unary_instructions.cc
@@ -297,6 +297,7 @@
     rv_vector->set_vector_exception();
     return;
   }
+  int vlen = rv_vector->vector_length();
   auto src_op = static_cast<RV32VectorSourceOperand*>(inst->Source(0));
   auto src_span = src_op->GetRegister(0)->data_buffer()->Get<uint8_t>();
   auto mask_op = static_cast<RV32VectorSourceOperand*>(inst->Source(1));
@@ -305,11 +306,10 @@
       static_cast<RV32VectorDestinationOperand*>(inst->Destination(0));
   auto* dest_db = dest_op->CopyDataBuffer(0);
   auto dest_span = dest_db->Get<uint8_t>();
-  int physical_bits = dest_span.size() * 8;
   bool before_first = true;
   int last = 0;
   // Set the bits before the first active 1.
-  for (int i = 0; i < physical_bits; i++) {
+  for (int i = 0; i < vlen; i++) {
     last = i;
     int index = i >> 3;
     int offset = i & 0b111;
@@ -322,13 +322,11 @@
       dest_span[index] |= 1 << offset;
     }
   }
-  for (int i = last; !before_first && (i < physical_bits); i++) {
+  // Clear the remaining bits.
+  for (int i = last; !before_first && (i < vlen); i++) {
     int index = i >> 3;
     int offset = i & 0b111;
-    int mask_value = (mask_span[index] >> offset) & 0b1;
-    if (mask_value) {
-      dest_span[index] &= ~(1 << offset);
-    }
+    dest_span[index] &= ~(1 << offset);
   }
   dest_db->Submit();
   rv_vector->clear_vstart();
@@ -341,6 +339,7 @@
     rv_vector->set_vector_exception();
     return;
   }
+  int vlen = rv_vector->vector_length();
   auto src_op = static_cast<RV32VectorSourceOperand*>(inst->Source(0));
   auto src_span = src_op->GetRegister(0)->data_buffer()->Get<uint8_t>();
   auto mask_op = static_cast<RV32VectorSourceOperand*>(inst->Source(1));
@@ -349,9 +348,8 @@
       static_cast<RV32VectorDestinationOperand*>(inst->Destination(0));
   auto* dest_db = dest_op->CopyDataBuffer(0);
   auto dest_span = dest_db->Get<uint8_t>();
-  int physical_bits = dest_span.size() * 8;
   uint8_t value = 1;
-  for (int i = 0; i < physical_bits; i++) {
+  for (int i = 0; i < vlen; i++) {
     int index = i >> 3;
     int offset = i & 0b111;
     int mask_value = (mask_span[index] >> offset) & 0b1;
@@ -378,6 +376,7 @@
     rv_vector->set_vector_exception();
     return;
   }
+  int vlen = rv_vector->vector_length();
   auto src_op = static_cast<RV32VectorSourceOperand*>(inst->Source(0));
   auto src_span = src_op->GetRegister(0)->data_buffer()->Get<uint8_t>();
   auto mask_op = static_cast<RV32VectorSourceOperand*>(inst->Source(1));
@@ -387,9 +386,8 @@
 
   auto* dest_db = dest_op->CopyDataBuffer(0);
   auto dest_span = dest_db->Get<uint8_t>();
-  int physical_bits = dest_span.size() * 8;
   bool first = true;
-  for (int i = 0; i < physical_bits; i++) {
+  for (int i = 0; i < vlen; i++) {
     int index = i >> 3;
     int offset = i & 0b111;
     int mask_value = (mask_span[index] >> offset) & 0b1;
diff --git a/riscv/test/riscv_vector_opm_instructions_test.cc b/riscv/test/riscv_vector_opm_instructions_test.cc
index 8c8070d..6bcda8d 100644
--- a/riscv/test/riscv_vector_opm_instructions_test.cc
+++ b/riscv/test/riscv_vector_opm_instructions_test.cc
@@ -102,10 +102,19 @@
     FillArrayWithRandomValues<uint8_t>(vd_value);
     AppendVectorRegisterOperands({kVs2, kVs1}, {kVd});
     for (int vstart : {0, 7, 32, 100, 250, 384}) {
-      for (int vlen_pct : {10, 20, 50, 100}) {
-        int vlen =
-            (kVectorLengthInBytes * 8 - vstart) * vlen_pct / 100 + vstart;
-        CHECK_LE(vlen, kVectorLengthInBytes * 8);
+      std::vector<int> test_vlens = {
+          0,
+          vstart,
+          vstart + 1,
+          vstart + 3,
+          vstart + 7,
+          (kVectorLengthInBytes * 8 - vstart) * 10 / 100 + vstart,
+          (kVectorLengthInBytes * 8 - vstart) * 20 / 100 + vstart,
+          (kVectorLengthInBytes * 8 - vstart) * 50 / 100 + vstart,
+          (kVectorLengthInBytes * 8 - vstart) * 100 / 100 + vstart,
+      };
+      for (int vlen : test_vlens) {
+        if (vlen > kVectorLengthInBytes * 8) continue;
         // Configure vector unit for different lmul settings.
         uint32_t vtype = (kSewSettingsByByteSize[1] << 3) | kLmulSettings[6];
         ConfigureVectorUnit(vtype, vlen);
@@ -120,7 +129,7 @@
           int mask_index = i >> 3;
           int mask_offset = i & 0b111;
           bool result = (dst_span[mask_index] >> mask_offset) & 0b1;
-          if (i < vstart) {
+          if ((i < vstart) || (i >= vlen)) {
             bool vd = (vd_value[mask_index] >> mask_offset) & 0b1;
             EXPECT_EQ(result, vd) << "[" << i << "] " << std::hex
                                   << "vd: " << (int)vd_value[mask_index]