diff --git a/compiler/compiler.go b/compiler/compiler.go
index 8707e1bc9..a4c2d2e8a 100644
--- a/compiler/compiler.go
+++ b/compiler/compiler.go
@@ -873,6 +873,10 @@ func (c *compilerContext) createPackage(irbuilder llvm.Builder, pkg *ssa.Package
 				// with a LLVM intrinsic.
 				continue
 			}
+			if ok := b.defineCryptoIntrinsic(); ok {
+				// Body of this function was replaced
+				continue
+			}
 			if member.Blocks == nil {
 				// Try to define this as an intrinsic function.
 				b.defineIntrinsicFunction()
diff --git a/compiler/intrinsics.go b/compiler/intrinsics.go
index d9d8bba5b..e60d16ebf 100644
--- a/compiler/intrinsics.go
+++ b/compiler/intrinsics.go
@@ -208,6 +208,23 @@ func (b *builder) defineMathOp() {
 	b.CreateRet(result)
 }
 
+func (b *builder) defineCryptoIntrinsic() bool {
+	if b.fn.Pkg.Pkg.Path() != "crypto/internal/constanttime" {
+		return false
+	}
+
+	switch b.fn.Name() {
+	case "boolToUint8":
+		b.createFunctionStart(true)
+		param := b.getValue(b.fn.Params[0], b.fn.Pos())
+		result := b.CreateZExt(param, b.ctx.Int8Type(), "")
+		b.CreateRet(result)
+		return true
+	}
+
+	return false
+}
+
 // Implement most math/bits functions.
 //
 // This implements all the functions that operate on bits. It does not yet