diff --git a/gen/optimizer.cpp b/gen/optimizer.cpp
index 76b53569..b0eef1d7 100644
--- a/gen/optimizer.cpp
+++ b/gen/optimizer.cpp
@@ -80,10 +80,12 @@ disableSimplifyDruntimeCalls("disable-simplify-drtcalls",
     cl::desc("Disable simplification of druntime calls"),
     cl::ZeroOrMore);
 
+#if LDC_LLVM_VER < 304
 static cl::opt<bool>
 disableSimplifyLibCalls("disable-simplify-libcalls",
     cl::desc("Disable simplification of well-known C runtime calls"),
     cl::ZeroOrMore);
+#endif
 
 static cl::opt<bool>
 disableGCToStack("disable-gc2stack",
@@ -179,7 +181,9 @@ static void addOptimizationPasses(PassManagerBase &mpm, FunctionPassManager &fpm
     } else {
         builder.Inliner = createAlwaysInlinerPass();
     }
+#if LDC_LLVM_VER < 304
     builder.DisableSimplifyLibCalls = disableSimplifyLibCalls;
+#endif
     builder.DisableUnitAtATime = !unitAtATime;
     builder.DisableUnrollLoops = optLevel == 0;
     /* builder.Vectorize is set in ctor from command line switch */
@@ -211,9 +215,11 @@ bool ldc_optimize_module(llvm::Module* m)
     // Add an appropriate TargetLibraryInfo pass for the module's triple.
     TargetLibraryInfo *tli = new TargetLibraryInfo(Triple(m->getTargetTriple()));
 
+#if LDC_LLVM_VER < 304
     // The -disable-simplify-libcalls flag actually disables all builtin optzns.
     if (disableSimplifyLibCalls)
         tli->disableAllFunctions();
+#endif
     mpm.add(tli);
 
     // Add an appropriate TargetData instance for this module.