diff --git a/.travis.yml b/.travis.yml
index b0623c38c..e99bbd848 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -28,6 +28,7 @@ cache:
 before_install:
 # Perl modules needed for testing
 # Not listing Bit::Vector as slow to install, and only skips one test
+  - touch temp.cpp ; g++ -E -dM -c temp.cpp | sort ; rm -rf temp.cpp
   - yes yes | sudo cpan -fi Unix::Processors Parallel::Forker
   - sudo apt-get install gdb gtkwave
   - sudo apt-get install libgoogle-perftools-dev
diff --git a/include/verilated.mk.in b/include/verilated.mk.in
index 0a5254610..47e3f61a9 100644
--- a/include/verilated.mk.in
+++ b/include/verilated.mk.in
@@ -114,9 +114,16 @@ endif
 #######################################################################
 ##### Threaded builds
 
+ifneq ($(VM_C11),0)
+ ifneq ($(VM_C11),)
+  VK_C11=1
+ endif
+endif
+
 ifneq ($(VM_THREADS),0)
  ifneq ($(VM_THREADS),)
   CPPFLAGS += -DVL_THREADED
+  VK_C11=1
   VK_LIBS_THREADED=1
  endif
 endif
@@ -124,14 +131,20 @@ endif
 ifneq ($(VM_TRACE_THREADED),0)
  ifneq ($(VM_TRACE_THREADED),)
   CPPFLAGS += -DVL_TRACE_THREADED
+  VK_C11=1
   VK_LIBS_THREADED=1
  endif
 endif
 
+ifneq ($(VK_C11),0)
+ ifneq ($(VK_C11),)
+  # Need C++11 at least, so always default to newest
+  CPPFLAGS += $(CFG_CXXFLAGS_STD_NEWEST)
+ endif
+endif
+
 ifneq ($(VK_LIBS_THREADED),0)
  ifneq ($(VK_LIBS_THREADED),)
-  # Need C++11 at least, so always default to newest
-  CPPFLAGS += $(CFG_CXXFLAGS_STD_NEWEST)
   LDLIBS += $(CFG_LDLIBS_THREADS)
  endif
 endif
diff --git a/src/V3EmitMk.cpp b/src/V3EmitMk.cpp
index 9efdad47f..e6147acf4 100644
--- a/src/V3EmitMk.cpp
+++ b/src/V3EmitMk.cpp
@@ -45,6 +45,8 @@ public:
         of.puts("# See "+v3Global.opt.prefix()+".mk"+" for the caller.\n");
 
         of.puts("\n### Switches...\n");
+        of.puts("# C11 constructs required?  0/1 (from --threads or use of classes)\n");
+        of.puts("VM_C11 = " + cvtToStr(v3Global.needC11() || v3Global.opt.threads()) + "\n");
         of.puts("# Coverage output mode?  0/1 (from --coverage)\n");
         of.puts("VM_COVERAGE = "); of.puts(v3Global.opt.coverage()?"1":"0"); of.puts("\n");
         of.puts("# Parallel builds?  0/1 (from --output-split)\n");
diff --git a/src/V3Global.h b/src/V3Global.h
index d97c20274..5c9503032 100644
--- a/src/V3Global.h
+++ b/src/V3Global.h
@@ -73,9 +73,10 @@ class V3Global {
     int m_debugFileNumber;  // Number to append to debug files created
     bool m_assertDTypesResolved;  // Tree should have dtypep()'s
     bool m_constRemoveXs;  // Const needs to strip any Xs
-    bool m_needTraceDumper;  // Need __Vm_dumperp in symbols
+    bool m_needC11;  // Need C++11
     bool m_needHInlines;  // Need __Inlines file
     bool m_needHeavy;  // Need verilated_heavy.h include
+    bool m_needTraceDumper;  // Need __Vm_dumperp in symbols
     bool m_dpi;  // Need __Dpi include files
 
 public:
@@ -89,9 +90,10 @@ public:
         m_widthMinUsage = VWidthMinUsage::LINT_WIDTH;
         m_assertDTypesResolved = false;
         m_constRemoveXs = false;
-        m_needTraceDumper = false;
+        m_needC11 = false;
         m_needHInlines = false;
         m_needHeavy = false;
+        m_needTraceDumper = false;
         m_dpi = false;
         m_rootp = NULL;  // created by makeInitNetlist() so static constructors run first
     }
@@ -117,12 +119,14 @@ public:
         char digits[100]; sprintf(digits, "%03d", m_debugFileNumber);
         return opt.makeDir()+"/"+opt.prefix()+"_"+digits+"_"+nameComment;
     }
-    bool needTraceDumper() const { return m_needTraceDumper; }
-    void needTraceDumper(bool flag) { m_needTraceDumper = flag; }
+    bool needC11() const { return m_needC11; }
+    void needC11(bool flag) { m_needC11 = flag; }
     bool needHInlines() const { return m_needHInlines; }
     void needHInlines(bool flag) { m_needHInlines = flag; }
     bool needHeavy() const { return m_needHeavy; }
     void needHeavy(bool flag) { m_needHeavy = flag; }
+    bool needTraceDumper() const { return m_needTraceDumper; }
+    void needTraceDumper(bool flag) { m_needTraceDumper = flag; }
     bool dpi() const { return m_dpi; }
     void dpi(bool flag) { m_dpi = flag; }
 };