diff --git a/src/V3Const.cpp b/src/V3Const.cpp
index 7a9abf574..dbe81ed4a 100644
--- a/src/V3Const.cpp
+++ b/src/V3Const.cpp
@@ -1162,11 +1162,10 @@ class ConstVisitor final : public VNVisitor {
         } else if (const AstShiftL* const shiftp = VN_CAST(nodep->rhsp(), ShiftL)) {
             if (const AstConst* const scp = VN_CAST(shiftp->rhsp(), Const)) {
                 // Check if mask is full over the non-zero bits
-                V3Number maskLo{nodep, nodep->width()};
-                V3Number maskHi{nodep, nodep->width()};
-                maskLo.setMask(nodep->width() - scp->num().toUInt());
-                maskHi.opShiftL(maskLo, scp->num());
-                return checkMask(maskHi);
+                V3Number mask{nodep, nodep->width()};
+                const uint32_t shiftAmount = scp->num().toUInt();
+                mask.setMask(nodep->width() - shiftAmount, shiftAmount);
+                return checkMask(mask);
             }
         }
         return false;
diff --git a/src/V3Delayed.cpp b/src/V3Delayed.cpp
index 8798aa151..aebf30b62 100644
--- a/src/V3Delayed.cpp
+++ b/src/V3Delayed.cpp
@@ -531,10 +531,7 @@ class DelayedVisitor final : public VNVisitor {
                         // Constant mask we can compute here
                         if (AstConst* const cLsbp = VN_CAST(sLsbp, Const)) {
                             AstConst* const cp = new AstConst{flp, AstConst::DTyped{}, eDTypep};
-                            cp->num().setAllBits0();
-                            const int lsb = cLsbp->toSInt();
-                            const int msb = lsb + sWidthp->toSInt() - 1;
-                            for (int bit = lsb; bit <= msb; ++bit) cp->num().setBit(bit, '1');
+                            cp->num().setMask(sWidthp->toSInt(), cLsbp->toSInt());
                             return cp;
                         }
 
diff --git a/src/V3Expand.cpp b/src/V3Expand.cpp
index 1ea5bf865..efe51bed3 100644
--- a/src/V3Expand.cpp
+++ b/src/V3Expand.cpp
@@ -551,7 +551,7 @@ class ExpandVisitor final : public VNVisitor {
             const int lsb = lhsp->lsbConst();
             const int msb = lhsp->msbConst();
             V3Number maskset{nodep, destp->widthMin()};
-            for (int bit = lsb; bit < (msb + 1); bit++) maskset.setBit(bit, 1);
+            maskset.setMask(msb + 1 - lsb, lsb);
             V3Number maskold{nodep, destp->widthMin()};
             maskold.opNot(maskset);
             if (destwide) {
@@ -654,7 +654,7 @@ class ExpandVisitor final : public VNVisitor {
                 fixCloneLvalue(oldvalp);
 
                 V3Number maskwidth{nodep, destp->widthMin()};
-                for (int bit = 0; bit < lhsp->widthConst(); bit++) maskwidth.setBit(bit, 1);
+                maskwidth.setMask(lhsp->widthConst());
 
                 if (destp->isQuad() && !rhsp->isQuad()) rhsp = new AstCCast{nfl, rhsp, nodep};
                 if (!ones) {
diff --git a/src/V3Number.cpp b/src/V3Number.cpp
index bb59c39bb..c446947aa 100644
--- a/src/V3Number.cpp
+++ b/src/V3Number.cpp
@@ -511,9 +511,9 @@ V3Number& V3Number::setValue1() {
     return *this;
 }
 
-V3Number& V3Number::setMask(int nbits) {
+V3Number& V3Number::setMask(int nbits, int lsb) {
     setZero();
-    for (int bit = 0; bit < nbits; bit++) setBit(bit, 1);
+    for (int bit = lsb; bit < lsb + nbits; bit++) setBit(bit, 1);
     return *this;
 }
 
diff --git a/src/V3Number.h b/src/V3Number.h
index c62a631e7..19b449ca3 100644
--- a/src/V3Number.h
+++ b/src/V3Number.h
@@ -576,7 +576,8 @@ public:
     V3Number& setAllBits0();
     V3Number& setAllBits1();
     V3Number& setValue1();
-    V3Number& setMask(int nbits);  // IE if nbits=1, then 0b1, if 2->0b11, if 3->0b111 etc
+    // IE if nbits=1, then 0b1, if 2->0b11, if 3->0b111 etc
+    V3Number& setMask(int nbits, int lsb = 0);
 
     // ACCESSORS
     string ascii(bool prefixed = true, bool cleanVerilog = false) const VL_MT_STABLE;