diff --git a/bin/verilator b/bin/verilator
index 12e52611c..534c1a9d6 100755
--- a/bin/verilator
+++ b/bin/verilator
@@ -964,9 +964,11 @@ If the design is not to be completely Verilated see also the --bbox-sys and
 --bbox-unsup options.
 
 =item --MMD
+=item --no-MMD
 
-Enable creation of .d dependency files, used for make dependency detection,
-similar to gcc -MMD option.  On by default, use --no-MMD to disable.
+Enable/disable creation of .d dependency files, used for make dependency
+detection, similar to gcc -MMD option.  By default this option is enabled
+for --cc or --sp modes.
 
 =item --MP
 
@@ -1017,9 +1019,11 @@ with extra loads and stores to handle the (imaginary) aliasing. Using only
 'vlTOPp->' references allows these old compilers to produce tight code.
 
 =item --no-skip-identical
+=item --skip-identical
 
-Rarely needed.  Disables skipping execution of Verilator if all source
-files are identical, and all output files exist with newer dates.
+Rarely needed.  Disables or enables skipping execution of Verilator if all
+source files are identical, and all output files exist with newer dates.
+By default this option is enabled for --cc or --sp modes only.
 
 =item +notimingchecks
 
diff --git a/src/V3Options.cpp b/src/V3Options.cpp
index 59e1ae399..b3c28eb60 100644
--- a/src/V3Options.cpp
+++ b/src/V3Options.cpp
@@ -528,11 +528,12 @@ string V3Options::getenvVERILATOR_ROOT() {
 void V3Options::notify() {
     // Notify that all arguments have been passed and final modification can be made.
     if (!outFormatOk()
-        && !preprocOnly()
+        && !cdc()
+        && !dpiHdrOnly()
         && !lintOnly()
-        && !xmlOnly()
-        && !cdc()) {
-        v3fatal("verilator: Need --cc, --sc, --cdc, --lint-only, --xml_only or --E option");
+        && !preprocOnly()
+        && !xmlOnly()) {
+        v3fatal("verilator: Need --cc, --sc, --cdc, --dpi-hdr-only, --lint-only, --xml-only or --E option");
     }
 
     // Make sure at least one make system is enabled
@@ -559,6 +560,22 @@ void V3Options::notify() {
                           +V3Error::warnMore()+"... Suggest remove --vpi.");
         }
     }
+
+    // Default some options if not turned on or off
+    if (v3Global.opt.skipIdentical().isDefault()) {
+        v3Global.opt.m_skipIdentical.setTrueOrFalse(
+            !v3Global.opt.cdc()
+            && !v3Global.opt.dpiHdrOnly()
+            && !v3Global.opt.lintOnly()
+            && !v3Global.opt.preprocOnly());
+    }
+    if (v3Global.opt.makeDepend().isDefault()) {
+        v3Global.opt.m_makeDepend.setTrueOrFalse(
+            !v3Global.opt.cdc()
+            && !v3Global.opt.dpiHdrOnly()
+            && !v3Global.opt.lintOnly()
+            && !v3Global.opt.preprocOnly());
+    }
 }
 
 //######################################################################
@@ -638,6 +655,15 @@ bool V3Options::onoff(const char* sw, const char* arg, bool& flag) {
     else if (0==strncmp(sw, "-no-", 4) && (0==strcmp(sw+4, arg+1))) { flag = false; return true; }
     return false;
 }
+bool V3Options::onoffb(const char* sw, const char* arg, VOptionBool& bflag) {
+    bool flag;
+    if (onoff(sw, arg, flag/*ref*/)) {
+        bflag.setTrueOrFalse(flag);
+        return true;
+    } else {
+        return false;
+    }
+}
 
 bool V3Options::suffixed(const string& sw, const char* arg) {
     if (strlen(arg) > sw.length()) return false;
@@ -696,12 +722,13 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc, char
         else if (argv[i][0]=='-') {
             const char *sw = argv[i];
             bool flag = true;
+            VOptionBool bflag;
             // Allow gnu -- switches
             if (sw[0]=='-' && sw[1]=='-') ++sw;
             if (0) {}
             // Single switches
             else if (!strcmp(sw, "-E"))                         { m_preprocOnly = true; }
-            else if ( onoff (sw, "-MMD", flag/*ref*/))          { m_makeDepend = flag; }
+            else if ( onoffb(sw, "-MMD", bflag/*ref*/))         { m_makeDepend = bflag; }
             else if ( onoff (sw, "-MP", flag/*ref*/))           { m_makePhony = flag; }
             else if (!strcmp(sw, "-P"))                         { m_preprocNoLine = true; }
             else if ( onoff (sw, "-assert", flag/*ref*/))       { m_assert = flag; }
@@ -748,13 +775,13 @@ void V3Options::parseOptsList(FileLine* fl, const string& optdir, int argc, char
             else if ( onoff (sw, "-protect-ids", flag/*ref*/))       { m_protectIds = flag; }
             else if ( onoff (sw, "-public", flag/*ref*/))            { m_public = flag; }
             else if ( onoff (sw, "-public-flat-rw", flag/*ref*/) )   { m_publicFlatRW = flag; v3Global.dpi(true); }
-            else if (!strncmp(sw, "-pvalue+", strlen("-pvalue+")))     { addParameter(string(sw+strlen("-pvalue+")), false); }
+            else if (!strncmp(sw, "-pvalue+", strlen("-pvalue+")))   { addParameter(string(sw+strlen("-pvalue+")), false); }
             else if ( onoff (sw, "-relative-cfuncs", flag/*ref*/))   { m_relativeCFuncs = flag; }
             else if ( onoff (sw, "-relative-includes", flag/*ref*/)) { m_relativeIncludes = flag; }
             else if ( onoff (sw, "-report-unoptflat", flag/*ref*/))  { m_reportUnoptflat = flag; }
             else if ( onoff (sw, "-savable", flag/*ref*/))           { m_savable = flag; }
             else if (!strcmp(sw, "-sc"))                             { m_outFormatOk = true; m_systemC = true; }
-            else if ( onoff (sw, "-skip-identical", flag/*ref*/))    { m_skipIdentical = flag; }
+            else if ( onoffb(sw, "-skip-identical", bflag/*ref*/))   { m_skipIdentical = bflag; }
             else if ( onoff (sw, "-stats", flag/*ref*/))             { m_stats = flag; }
             else if ( onoff (sw, "-stats-vars", flag/*ref*/))        { m_statsVars = flag; m_stats |= flag; }
             else if (!strcmp(sw, "-sv"))                             { m_defaultLanguage = V3LangCode::L1800_2005; }
@@ -1420,7 +1447,6 @@ V3Options::V3Options() {
     m_inhibitSim = false;
     m_lintOnly = false;
     m_gmake = false;
-    m_makeDepend = true;
     m_makePhony = false;
     m_orderClockDly = true;
     m_outFormatOk = false;
@@ -1440,7 +1466,6 @@ V3Options::V3Options() {
     m_relativeIncludes = false;
     m_reportUnoptflat = false;
     m_savable = false;
-    m_skipIdentical = true;
     m_stats = false;
     m_statsVars = false;
     m_systemC = false;
diff --git a/src/V3Options.h b/src/V3Options.h
index 465f164c4..61f428837 100644
--- a/src/V3Options.h
+++ b/src/V3Options.h
@@ -37,6 +37,39 @@ class FileLine;
 
 //######################################################################
 
+class VOptionBool {
+    // Class to track options that are either not specified (and default
+    // true/false), versus user setting the option to true or false
+public:
+    enum en {
+        OPT_DEFAULT_FALSE = 0,
+        OPT_DEFAULT_TRUE,
+        OPT_TRUE,
+        OPT_FALSE,
+        _ENUM_END
+    };
+    enum en m_e;
+    inline VOptionBool() : m_e(OPT_DEFAULT_FALSE) {}
+    // cppcheck-suppress noExplicitConstructor
+    inline VOptionBool(en _e) : m_e(_e) {}
+    explicit inline VOptionBool(int _e) : m_e(static_cast<en>(_e)) {}
+    operator en() const { return m_e; }
+    bool isDefault() const { return m_e == OPT_DEFAULT_FALSE || m_e == OPT_DEFAULT_TRUE; }
+    bool isTrue() const { return m_e == OPT_TRUE || m_e == OPT_DEFAULT_TRUE; }
+    bool isFalse() const { return m_e == OPT_FALSE || m_e == OPT_DEFAULT_FALSE; }
+    void setTrueOrFalse(bool flag) { m_e = flag ? OPT_TRUE : OPT_FALSE; }
+    const char* ascii() const {
+        static const char* const names[] = {
+            "DEFAULT_FALSE", "DEFAULT_TRUE", "TRUE", "FALSE"};
+        return names[m_e]; }
+  };
+  inline bool operator==(VOptionBool lhs, VOptionBool rhs) { return (lhs.m_e == rhs.m_e); }
+  inline bool operator==(VOptionBool lhs, VOptionBool::en rhs) { return (lhs.m_e == rhs); }
+  inline bool operator==(VOptionBool::en lhs, VOptionBool rhs) { return (lhs == rhs.m_e); }
+  inline std::ostream& operator<<(std::ostream& os, const VOptionBool& rhs) { return os<<rhs.ascii(); }
+
+//######################################################################
+
 class TraceFormat {
 public:
     enum en {
@@ -101,7 +134,6 @@ class V3Options {
 
 
     bool        m_preprocOnly;  // main switch: -E
-    bool        m_makeDepend;   // main switch: -MMD
     bool        m_makePhony;    // main switch: -MP
     bool        m_preprocNoLine;// main switch: -P
     bool        m_assert;       // main switch: --assert
@@ -145,7 +177,6 @@ class V3Options {
     bool        m_reportUnoptflat; // main switch: --report-unoptflat
     bool        m_savable;      // main switch: --savable
     bool        m_systemC;      // main switch: --sc: System C instead of simple C++
-    bool        m_skipIdentical;// main switch: --skip-identical
     bool        m_stats;        // main switch: --stats
     bool        m_statsVars;    // main switch: --stats-vars
     bool        m_threadsCoarsen;  // main switch: --threads-coarsen
@@ -167,11 +198,13 @@ class V3Options {
     int         m_gateStmts;    // main switch: --gate-stmts
     int         m_ifDepth;      // main switch: --if-depth
     int         m_inlineMult;   // main switch: --inline-mult
+    VOptionBool m_makeDepend;  // main switch: -MMD
     int         m_moduleRecursion;// main switch: --module-recursion-depth
     int         m_outputSplit;  // main switch: --output-split
     int         m_outputSplitCFuncs;// main switch: --output-split-cfuncs
     int         m_outputSplitCTrace;// main switch: --output-split-ctrace
     int         m_pinsBv;       // main switch: --pins-bv
+    VOptionBool m_skipIdentical;  // main switch: --skip-identical
     int         m_threads;      // main switch: --threads (0 == --no-threads)
     int         m_threadsMaxMTasks;  // main switch: --threads-max-mtasks
     int         m_traceDepth;   // main switch: --trace-depth
@@ -239,6 +272,7 @@ class V3Options {
     void showVersion(bool verbose);
     void coverage(bool flag) { m_coverageLine = m_coverageToggle = m_coverageUser = flag; }
     bool onoff(const char* sw, const char* arg, bool& flag);
+    bool onoffb(const char* sw, const char* arg, VOptionBool& flag);
     bool suffixed(const string& sw, const char* arg);
     string parseFileArg(const string& optdir, const string& relfilename);
     bool parseLangExt(const char* swp, const char* langswp, const V3LangCode& lc);
@@ -268,7 +302,6 @@ class V3Options {
 
     // ACCESSORS (options)
     bool preprocOnly() const { return m_preprocOnly; }
-    bool makeDepend() const { return m_makeDepend; }
     bool makePhony() const { return m_makePhony; }
     bool preprocNoLine() const { return m_preprocNoLine; }
     bool underlineZero() const { return m_underlineZero; }
@@ -277,7 +310,6 @@ class V3Options {
     bool systemC() const { return m_systemC; }
     bool usingSystemCLibs() const { return !lintOnly() && systemC(); }
     bool savable() const { return m_savable; }
-    bool skipIdentical() const { return m_skipIdentical; }
     bool stats() const { return m_stats; }
     bool statsVars() const { return m_statsVars; }
     bool assertOn() const { return m_assert; }  // assertOn as __FILE__ may be defined
@@ -338,11 +370,13 @@ class V3Options {
     int gateStmts() const { return m_gateStmts; }
     int ifDepth() const { return m_ifDepth; }
     int inlineMult() const { return m_inlineMult; }
+    VOptionBool makeDepend() const { return m_makeDepend; }
     int moduleRecursionDepth() const { return m_moduleRecursion; }
     int outputSplit() const { return m_outputSplit; }
     int outputSplitCFuncs() const { return m_outputSplitCFuncs; }
     int outputSplitCTrace() const { return m_outputSplitCTrace; }
     int pinsBv() const { return m_pinsBv; }
+    VOptionBool skipIdentical() const { return m_skipIdentical; }
     int threads() const { return m_threads; }
     int threadsMaxMTasks() const { return m_threadsMaxMTasks; }
     bool mtasks() const { return (m_threads > 1); }
diff --git a/src/Verilator.cpp b/src/Verilator.cpp
index 99efc6830..c01728dd7 100644
--- a/src/Verilator.cpp
+++ b/src/Verilator.cpp
@@ -607,10 +607,7 @@ int main(int argc, char** argv, char** env) {
 
     // Can we skip doing everything if times are ok?
     V3File::addSrcDepend(v3Global.opt.bin());
-    if (v3Global.opt.skipIdentical()
-        && !v3Global.opt.preprocOnly()
-        && !v3Global.opt.lintOnly()
-        && !v3Global.opt.cdc()
+    if (v3Global.opt.skipIdentical().isTrue()
         && V3File::checkTimes(v3Global.opt.makeDir()+"/"+v3Global.opt.prefix()
                               +"__verFiles.dat", argString)) {
         UINFO(1,"--skip-identical: No change to any source files, exiting\n");
@@ -648,13 +645,10 @@ int main(int argc, char** argv, char** env) {
     V3Global::dumpCheckGlobalTree("final", 990, v3Global.opt.dumpTreeLevel(__FILE__) >= 3);
     V3Error::abortIfWarnings();
 
-    if (!v3Global.opt.lintOnly() && !v3Global.opt.cdc()
-        && !v3Global.opt.dpiHdrOnly() && v3Global.opt.makeDepend()) {
+    if (v3Global.opt.makeDepend().isTrue()) {
         V3File::writeDepend(v3Global.opt.makeDir()+"/"+v3Global.opt.prefix()+"__ver.d");
     }
-    if (!v3Global.opt.lintOnly() && !v3Global.opt.cdc()
-        && !v3Global.opt.dpiHdrOnly()
-        && (v3Global.opt.skipIdentical() || v3Global.opt.makeDepend())) {
+    if (v3Global.opt.skipIdentical().isTrue() || v3Global.opt.makeDepend().isTrue()) {
         V3File::writeTimes(v3Global.opt.makeDir()+"/"+v3Global.opt.prefix()
                            +"__verFiles.dat", argString);
     }
diff --git a/test_regress/t/t_dpi_import_hdr_only.pl b/test_regress/t/t_dpi_import_hdr_only.pl
index cce0dcf8b..a884ce466 100755
--- a/test_regress/t/t_dpi_import_hdr_only.pl
+++ b/test_regress/t/t_dpi_import_hdr_only.pl
@@ -17,14 +17,15 @@ top_filename("t/t_dpi_import.v");
 my $tmp_dir = File::Temp->newdir();
 
 compile(
-    verilator_flags2 => ["-Wall -Wno-DECLFILENAME -Mdir " . $tmp_dir . " --dpi-hdr-only"],
+    # Override default flags also
+    verilator_flags => ["-Wall -Wno-DECLFILENAME -Mdir " . $tmp_dir . " --dpi-hdr-only"],
     verilator_make_gmake => 0,
     );
 
 my @files = glob($tmp_dir . "/*");
 
 error("Did not produce DPI header") if scalar(@files) == 0;
-error("Too many files created") if scalar(@files) > 1;
+error("Too many files created:".join(', ', @files)) if scalar(@files) > 1;
 
 my $tmp_header = $files[0];
 print("============".$tmp_header."\n");