diff --git a/README.md b/README.md
index a23dc14d..4c3682eb 100644
--- a/README.md
+++ b/README.md
@@ -107,7 +107,7 @@ builder.positionAtEnd(of: entryBB)
 let local = builder.buildAlloca(type: FloatType.double, name: "local")
 
 // Compare to the condition
-let test = builder.buildICmp(function.parameters[0], IntType.int1.zero(), .notEqual)
+let test = builder.buildICmp(function.parameters[0], IntType.int1.zero(), .equal)
 
 // Create basic blocks for "then", "else", and "merge"
 let thenBB = function.appendBasicBlock(named: "then")
diff --git a/Sources/LLVM/JIT.swift b/Sources/LLVM/JIT.swift
index 497bdde2..55261d99 100644
--- a/Sources/LLVM/JIT.swift
+++ b/Sources/LLVM/JIT.swift
@@ -32,6 +32,10 @@ public final class JIT {
   /// The underlying LLVMExecutionEngineRef backing this JIT.
   internal let llvm: LLVMExecutionEngineRef
 
+  private static var linkOnce: () = {
+    return LLVMLinkInMCJIT()
+  }()
+
   /// Creates a Just In Time compiler that will compile the code in the
   /// provided `Module` to the architecture of the provided `TargetMachine`,
   /// and execute it.
@@ -41,6 +45,8 @@ public final class JIT {
   ///   - machine: The target machine which you're compiling for
   /// - throws: JITError
   public init(module: Module, machine: TargetMachine) throws {
+    _ = JIT.linkOnce
+
     var jit: LLVMExecutionEngineRef?
     var error: UnsafeMutablePointer<Int8>?
     if LLVMCreateExecutionEngineForModule(&jit, module.llvm, &error) != 0 {
@@ -54,22 +60,6 @@ public final class JIT {
     LLVMRunStaticConstructors(self.llvm)
   }
 
-  /// Runs the specified function with the provided arguments by compiling
-  /// it to machine code for the target architecture used to initialize this
-  /// JIT.
-  ///
-  /// - parameters:
-  ///   - function: The function you wish to execute
-  ///   - args: The arguments you wish to pass to the function
-  /// - returns: The LLVM value that the function returned
-  public func runFunction(_ function: Function, args: [IRValue]) -> IRValue {
-    var irArgs = args.map { $0.asLLVM() as Optional }
-    return irArgs.withUnsafeMutableBufferPointer { buf in
-      return LLVMRunFunction(llvm, function.asLLVM(),
-                             UInt32(buf.count), buf.baseAddress)
-    }
-  }
-
   /// Retrieves a pointer to the function compiled by this JIT.
   /// - parameter name: The name of the function you wish to look up.
   /// - returns: A pointer to the result of compiling the specified function.
diff --git a/Tests/LLVMTests/JITSpec.swift b/Tests/LLVMTests/JITSpec.swift
new file mode 100644
index 00000000..c664b3d1
--- /dev/null
+++ b/Tests/LLVMTests/JITSpec.swift
@@ -0,0 +1,79 @@
+import LLVM
+import XCTest
+import FileCheck
+import Foundation
+
+class JITSpec : XCTestCase {
+  func testFibonacci() {
+    XCTAssert(fileCheckOutput(withPrefixes: ["JIT"]) {
+      let module = Module(name: "Fibonacci")
+      let builder = IRBuilder(module: module)
+
+      let function = builder.addFunction(
+        "calculateFibs",
+        type: FunctionType(argTypes: [IntType.int1],
+                           returnType: FloatType.double)
+      )
+      let entryBB = function.appendBasicBlock(named: "entry")
+      builder.positionAtEnd(of: entryBB)
+
+      // allocate space for a local value
+      let local = builder.buildAlloca(type: FloatType.double, name: "local")
+
+      // Compare to the condition
+      let test = builder.buildICmp(function.parameters[0], IntType.int1.zero(), .equal)
+
+      // Create basic blocks for "then", "else", and "merge"
+      let thenBB = function.appendBasicBlock(named: "then")
+      let elseBB = function.appendBasicBlock(named: "else")
+      let mergeBB = function.appendBasicBlock(named: "merge")
+
+      builder.buildCondBr(condition: test, then: thenBB, else: elseBB)
+
+      // MARK: Then Block
+
+      builder.positionAtEnd(of: thenBB)
+      // local = 1/89, the fibonacci series (sort of)
+      let thenVal = FloatType.double.constant(1/89)
+      // Branch to the merge block
+      builder.buildBr(mergeBB)
+
+      // MARK: Else Block
+      builder.positionAtEnd(of: elseBB)
+      // local = 1/109, the fibonacci series (sort of) backwards
+      let elseVal = FloatType.double.constant(1/109)
+      // Branch to the merge block
+      builder.buildBr(mergeBB)
+
+      // MARK: Merge Block
+
+      builder.positionAtEnd(of: mergeBB)
+      let phi = builder.buildPhi(FloatType.double, name: "phi_example")
+      phi.addIncoming([
+        (thenVal, thenBB),
+        (elseVal, elseBB),
+      ])
+      builder.buildStore(phi, to: local)
+      let ret = builder.buildLoad(local, name: "ret")
+      builder.buildRet(ret)
+
+      // Setup the JIT
+      let jit = try! JIT(module: module, machine: TargetMachine())
+      typealias FnPtr = @convention(c) (Bool) -> Double
+      // Retrieve a handle to the function we're going to invoke
+      let fnAddr = jit.addressOfFunction(name: "calculateFibs")
+      let fn = unsafeBitCast(fnAddr, to: FnPtr.self)
+      // JIT: 0.00917431192660551
+      print(fn(true))
+      // JIT-NEXT: 0.0112359550561798
+      print(fn(false))
+    })
+  }
+
+  #if !os(macOS)
+  static var allTests = testCase([
+    ("testFibonacci", testFibonacci),
+  ])
+  #endif
+}
+
diff --git a/Tests/LinuxMain.swift b/Tests/LinuxMain.swift
index f7bbade9..6d8a4267 100644
--- a/Tests/LinuxMain.swift
+++ b/Tests/LinuxMain.swift
@@ -9,5 +9,6 @@ XCTMain([
   IRExceptionSpec.allTests,
   IROperationSpec.allTests,
   FileCheckSpec.allTests,
+  JITSpec.allTests,
 ])
 #endif