diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4296b23..4255dc7 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,8 +38,7 @@
 add_cxx_compiler_flag(-Wshadow)
 add_cxx_compiler_flag(-Werror)
 add_cxx_compiler_flag(-pedantic-errors)
-# TODO(ericwf): enable this for g++
-#add_cxx_compiler_flag(-Wzero-as-null-pointer-constant)
+add_cxx_compiler_flag(-Wzero-as-null-pointer-constant)
 # Release flags
 add_cxx_compiler_flag(-fno-strict-aliasing RELEASE)
 
diff --git a/include/benchmark/benchmark.h b/include/benchmark/benchmark.h
index aa80bbc..f796dc3 100644
--- a/include/benchmark/benchmark.h
+++ b/include/benchmark/benchmark.h
@@ -152,7 +152,8 @@
 
 // Otherwise, run all benchmarks specified by the --benchmark_filter flag,
 // and exit after running the benchmarks.
-void RunSpecifiedBenchmarks(const BenchmarkReporter* reporter = NULL);
+void RunSpecifiedBenchmarks();
+void RunSpecifiedBenchmarks(const BenchmarkReporter* reporter);
 
 // If this routine is called, peak memory allocation past this point in the
 // benchmark is reported at the end of the benchmark report line. (It is
@@ -164,6 +165,19 @@
 namespace internal {
 class Benchmark;
 class BenchmarkFamilies;
+
+template <class T> struct Voider {
+    typedef void type;
+};
+
+template <class T, class = void>
+struct EnableIfString {};
+
+template <class T>
+struct EnableIfString<T, typename Voider<typename T::basic_string>::type> {
+    typedef int type;
+};
+
 }
 
 // State is passed to a running Benchmark and contains state for the
@@ -279,7 +293,7 @@
   // as an injected class name in the case of std::string.
   template <class StringType>
   void SetLabel(StringType const & str,
-                typename StringType::basic_string* = 0) {
+                typename internal::EnableIfString<StringType>::type = 1) {
     this->SetLabel(str.c_str());
   }
 
diff --git a/src/benchmark.cc b/src/benchmark.cc
index 8b0682e..82f5f5f 100644
--- a/src/benchmark.cc
+++ b/src/benchmark.cc
@@ -898,6 +898,9 @@
 
 } // end namespace internal
 
+void RunSpecifiedBenchmarks() {
+  RunSpecifiedBenchmarks(nullptr);
+}
 
 void RunSpecifiedBenchmarks(const BenchmarkReporter* reporter) {
   std::string spec = FLAGS_benchmark_filter;
diff --git a/src/sysinfo.cc b/src/sysinfo.cc
index ace7caa..b275360 100644
--- a/src/sysinfo.cc
+++ b/src/sysinfo.cc
@@ -303,7 +303,7 @@
     cputime_fd = -1;
     return false;
   }
-  unsigned long long result = strtoull(buff, NULL, 0);
+  unsigned long long result = strtoull(buff, nullptr, 0);
   if (result == (std::numeric_limits<unsigned long long>::max)()) {
     close(cputime_fd);
     cputime_fd = -1;
diff --git a/src/walltime.cc b/src/walltime.cc
index 39c0497..fa1b61f 100644
--- a/src/walltime.cc
+++ b/src/walltime.cc
@@ -89,7 +89,7 @@
 
   WallTime Slow() const {
     struct timeval tv;
-    gettimeofday(&tv, NULL);
+    gettimeofday(&tv, nullptr);
     return tv.tv_sec + tv.tv_usec * 1e-6;
   }