diff --git a/include/circt/Dialect/SV/SVExpressions.td b/include/circt/Dialect/SV/SVExpressions.td
index aa3b791bab..fe071f411e 100644
--- a/include/circt/Dialect/SV/SVExpressions.td
+++ b/include/circt/Dialect/SV/SVExpressions.td
@@ -25,3 +25,27 @@ def TextualValueOp : SVOp<"textual_value", [NoSideEffect]> {
   let results = (outs AnySignlessInteger:$result);
   let assemblyFormat = "$string attr-dict `:` type($result)";
 }
+
+def ConstantXOp : SVOp<"constantX", [NoSideEffect]> {
+  let summary = "A constant of value 'x'";
+  let description = [{
+    This operation produces a constant value of 'x'.  This 'x' follows the
+    System Verilog rules for 'x' propagation.
+    }];
+
+  let arguments = (ins);
+  let results = (outs RTLIntegerType:$result);
+  let assemblyFormat = " attr-dict `:` type($result)";
+}
+
+def ConstantZOp : SVOp<"constantZ", [NoSideEffect]> {
+  let summary = "A constant of value 'z'";
+  let description = [{
+    This operation produces a constant value of 'z'.  This 'z' follows the
+    System Verilog rules for 'z' propagation.
+    }];
+
+  let arguments = (ins);
+  let results = (outs RTLIntegerType:$result);
+  let assemblyFormat = " attr-dict `:` type($result)";
+}
diff --git a/include/circt/Dialect/SV/SVVisitors.h b/include/circt/Dialect/SV/SVVisitors.h
index 6e80792b9b..fedad56f5c 100644
--- a/include/circt/Dialect/SV/SVVisitors.h
+++ b/include/circt/Dialect/SV/SVVisitors.h
@@ -28,7 +28,8 @@ public:
     return TypeSwitch<Operation *, ResultType>(op)
         .template Case<
             // Expressions
-            ReadInOutOp, ArrayIndexInOutOp, TextualValueOp,
+            ReadInOutOp, ArrayIndexInOutOp, TextualValueOp, ConstantXOp,
+            ConstantZOp,
             // Declarations.
             RegOp, WireOp,
             // Control flow.
@@ -74,9 +75,11 @@ public:
   HANDLE(WireOp, Unhandled);
 
   // Expressions
-  HANDLE(TextualValueOp, Unhandled)
   HANDLE(ReadInOutOp, Unhandled);
   HANDLE(ArrayIndexInOutOp, Unhandled);
+  HANDLE(TextualValueOp, Unhandled);
+  HANDLE(ConstantXOp, Unhandled);
+  HANDLE(ConstantZOp, Unhandled);
 
   // Control flow.
   HANDLE(IfDefOp, Unhandled);
diff --git a/lib/Dialect/SV/SVOps.cpp b/lib/Dialect/SV/SVOps.cpp
index 8aba69c061..32a7678115 100644
--- a/lib/Dialect/SV/SVOps.cpp
+++ b/lib/Dialect/SV/SVOps.cpp
@@ -24,7 +24,8 @@ using namespace sv;
 /// Return true if the specified operation is an expression.
 bool sv::isExpression(Operation *op) {
   return isa<sv::TextualValueOp>(op) || isa<sv::GetModportOp>(op) ||
-         isa<sv::ReadInterfaceSignalOp>(op);
+         isa<sv::ReadInterfaceSignalOp>(op) || isa<sv::ConstantXOp>(op) ||
+         isa<sv::ConstantZOp>(op);
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/lib/Translation/ExportVerilog/ExportVerilog.cpp b/lib/Translation/ExportVerilog/ExportVerilog.cpp
index 134c40319b..3616c9b42d 100644
--- a/lib/Translation/ExportVerilog/ExportVerilog.cpp
+++ b/lib/Translation/ExportVerilog/ExportVerilog.cpp
@@ -722,6 +722,8 @@ private:
   SubExprInfo visitSV(GetModportOp op);
   SubExprInfo visitSV(ReadInterfaceSignalOp op);
   SubExprInfo visitSV(TextualValueOp op);
+  SubExprInfo visitSV(ConstantXOp op);
+  SubExprInfo visitSV(ConstantZOp op);
 
   // Noop cast operators.
   SubExprInfo visitSV(ReadInOutOp op) {
@@ -1104,6 +1106,16 @@ SubExprInfo ExprEmitter::visitSV(TextualValueOp op) {
   return {Unary, IsUnsigned};
 }
 
+SubExprInfo ExprEmitter::visitSV(ConstantXOp op) {
+  os << op.getType().getWidth() << "'bx";
+  return {Unary, IsUnsigned};
+}
+
+SubExprInfo ExprEmitter::visitSV(ConstantZOp op) {
+  os << op.getType().getWidth() << "'bz";
+  return {Unary, IsUnsigned};
+}
+
 SubExprInfo ExprEmitter::visitTypeOp(ConstantOp op) {
   bool isNegated = false;
   const APInt &value = op.getValue();
diff --git a/test/Dialect/SV/basic.mlir b/test/Dialect/SV/basic.mlir
index e44c65b23d..3ec65c8fb6 100644
--- a/test/Dialect/SV/basic.mlir
+++ b/test/Dialect/SV/basic.mlir
@@ -15,7 +15,9 @@ rtl.module @test1(%arg0: i1, %arg1: i1, %arg8: i8) {
     sv.ifdef "SYNTHESIS" {
     } else {
       %tmp = sv.textual_value "PRINTF_COND_" : i1
-      %tmp2 = comb.and %tmp, %arg1 : i1
+      %tmpx = sv.constantX : i1
+      %tmpz = sv.constantZ : i1
+      %tmp2 = comb.and %tmp, %tmpx, %tmpz, %arg1 : i1
       sv.if %tmp2 {
         sv.fwrite "Hi\n" 
       }
@@ -32,12 +34,14 @@ rtl.module @test1(%arg0: i1, %arg1: i1, %arg8: i8) {
   // CHECK-NEXT:   sv.ifdef "SYNTHESIS" {
   // CHECK-NEXT:   } else {
   // CHECK-NEXT:     %0 = sv.textual_value "PRINTF_COND_" : i1
-  // CHECK-NEXT:     %1 = comb.and %0, %arg1 : i1
-  // CHECK-NEXT:     sv.if %1 {
+  // CHECK-NEXT:     %1 = sv.constantX : i1
+  // CHECK-NEXT:     %2 = sv.constantZ : i1
+  // CHECK-NEXT:     %3 = comb.and %0, %1, %2, %arg1 : i1
+  // CHECK-NEXT:     sv.if %3 {
   // CHECK-NEXT:       sv.fwrite "Hi\0A" 
   // CHECK-NEXT:     }
-  // CHECK-NEXT:     sv.if %1 {
-  // CHECK-NEXT:       sv.fwrite "%x"(%1) : i1
+  // CHECK-NEXT:     sv.if %3 {
+  // CHECK-NEXT:       sv.fwrite "%x"(%3) : i1
   // CHECK-NEXT:     } else {
   // CHECK-NEXT:       sv.fwrite "There\0A" 
   // CHECK-NEXT:     }
diff --git a/test/ExportVerilog/sv-dialect.mlir b/test/ExportVerilog/sv-dialect.mlir
index 3c4ac019f5..2423b05685 100644
--- a/test/ExportVerilog/sv-dialect.mlir
+++ b/test/ExportVerilog/sv-dialect.mlir
@@ -9,18 +9,20 @@ rtl.module @M1(%clock : i1, %cond : i1, %val : i8) {
   sv.always posedge %clock {
     sv.ifdef "SYNTHESIS" {
     } else {
-  // CHECK-NEXT:     if (PRINTF_COND_ & cond)
+  // CHECK-NEXT:     if (PRINTF_COND_ & 1'bx & 1'bz & cond)
       %tmp = sv.textual_value "PRINTF_COND_" : i1
-      %tmp2 = comb.and %tmp, %cond : i1
-      sv.if %tmp2 {
+      %tmp1 = sv.constantX : i1
+      %tmp2 = sv.constantZ : i1
+      %tmp3 = comb.and %tmp, %tmp1, %tmp2, %cond : i1
+      sv.if %tmp3 {
   // CHECK-NEXT:       $fwrite(32'h80000002, "Hi\n");
         sv.fwrite "Hi\n"
       }
 
       // CHECK-NEXT: if (!(clock | cond))
       // CHECK-NEXT:   $fwrite(32'h80000002, "Bye\n");
-      %tmp3 = comb.or %clock, %cond : i1
-      sv.if %tmp3 {
+      %tmp4 = comb.or %clock, %cond : i1
+      sv.if %tmp4 {
       } else {
         sv.fwrite "Bye\n"
       }