diff --git a/Changes b/Changes
index 843fc5ae2..364efe718 100644
--- a/Changes
+++ b/Changes
@@ -14,6 +14,14 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Fix internals to avoid 'using namespace std'.
 
+****  Fix Verilation performance issues, bug1316. [John Coiner]
+
+
+* Verilator 3.925 devel
+
+
+* Verilator 3.924 2018-06-12
+
 ***   Renamed --profile-cfuncs to --prof-cfuncs.
 
 ****  Report interface ports connected to wrong interface, bug1294. [Todd Strader]
@@ -24,7 +32,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Fix parsing error on bad missing #, bug1308. [Dan Kirkham]
 
-****  Fix Verilation performance issues, bug1316. [John Coiner]
+****  Fix $clog2 to be in verilog 2005, bug1319. [James Hutchinson]
+
 
 * Verilator 3.922 2018-03-17
 
diff --git a/include/verilated.cpp b/include/verilated.cpp
index 1ad503beb..ae4fb1aeb 100644
--- a/include/verilated.cpp
+++ b/include/verilated.cpp
@@ -122,10 +122,16 @@ std::string _vl_string_vprintf(const char* formatp, va_list ap) VL_MT_SAFE {
     va_list aq;
     va_copy(aq, ap);
     int len = VL_VSNPRINTF(NULL, 0, formatp, aq);
-    if (VL_UNLIKELY(len < 1)) return "";
+    va_end(aq);
+    if (VL_UNLIKELY(len < 1)) {
+        va_end(ap);
+        return "";
+    }
 
     char* bufp = new char[len+1];
     VL_VSNPRINTF(bufp, len+1, formatp, ap);
+    va_end(ap);
+
     std::string out = std::string(bufp, len);
     delete[] bufp;
     return out;
@@ -163,7 +169,7 @@ void VL_DBG_MSGF(const char* formatp, ...) VL_MT_SAFE {
     // Using VL_PRINTF not VL_PRINTF_MT so that we can call VL_DBG_MSGF
     // from within the guts of the thread execution machinery (and it goes
     // to the screen and not into the queues we're debugging)
-    VL_PRINTF("-V{t%d,%" VL_PRI64 "d}%s", VL_THREAD_ID(), _vl_dbg_sequence_number(), out.c_str());
+    VL_PRINTF("-V{t%d,%" VL_PRI64 "u}%s", VL_THREAD_ID(), _vl_dbg_sequence_number(), out.c_str());
 }
 
 #ifdef VL_THREADED
diff --git a/include/verilated_vpi.cpp b/include/verilated_vpi.cpp
index c57bcad13..63faa7ecd 100644
--- a/include/verilated_vpi.cpp
+++ b/include/verilated_vpi.cpp
@@ -473,11 +473,12 @@ public:
         m_errorInfo.level = level;
         return this;
     }
-    void setMessage(std::string file, PLI_INT32 line, const std::string& message, ...) {
+    void setMessage(std::string file, PLI_INT32 line, const char* message, ...) {
+        // message cannot be a const string& as va_start cannot use a reference
         static VL_THREAD_LOCAL std::string filehold;
         va_list args;
         va_start(args, message);
-        VL_VSNPRINTF(m_buff, sizeof(m_buff), message.c_str(), args);
+        VL_VSNPRINTF(m_buff, sizeof(m_buff), message, args);
         va_end(args);
         m_errorInfo.state = vpiPLI;
         filehold = file;
diff --git a/src/V3Ast.h b/src/V3Ast.h
index c1489d7e4..c0b0cee97 100644
--- a/src/V3Ast.h
+++ b/src/V3Ast.h
@@ -2105,7 +2105,7 @@ public:
 class AstNodeRange : public AstNode {
     // A range, sized or unsized
 public:
-    AstNodeRange(FileLine* fl) : AstNode (fl) { }
+    explicit AstNodeRange(FileLine* fl) : AstNode (fl) { }
     ASTNODE_BASE_FUNCS(NodeRange)
 };
 
diff --git a/src/V3AstNodes.h b/src/V3AstNodes.h
index a2e775a78..327374a93 100644
--- a/src/V3AstNodes.h
+++ b/src/V3AstNodes.h
@@ -151,7 +151,7 @@ public:
 class AstUnsizedRange : public AstNodeRange {
     // Unsized range specification, for open arrays
 public:
-    AstUnsizedRange(FileLine* fl) : AstNodeRange(fl) { }
+    explicit AstUnsizedRange(FileLine* fl) : AstNodeRange(fl) { }
     ASTNODE_NODE_FUNCS(UnsizedRange)
     virtual string emitC() { V3ERROR_NA; return ""; }
     virtual string emitVerilog() { return "[]"; }
diff --git a/src/verilog.l b/src/verilog.l
index f116279a2..0d0ac40b3 100644
--- a/src/verilog.l
+++ b/src/verilog.l
@@ -422,6 +422,8 @@ vnum	{vnum1}|{vnum2}|{vnum3}|{vnum4}|{vnum5}
 
   /* Verilog 2005 */
 <V05,S05,S09,S12,S17,SAX>{
+  /*     System Tasks */
+  "$clog2"		{ FL; return yD_CLOG2; }
   /*     Keywords */
   "uwire"		{ FL; return yWIRE; }
 }
@@ -430,7 +432,6 @@ vnum	{vnum1}|{vnum2}|{vnum3}|{vnum4}|{vnum5}
 <S05,S09,S12,S17,SAX>{
   /*     System Tasks */
   "$bits"		{ FL; return yD_BITS; }
-  "$clog2"		{ FL; return yD_CLOG2; }
   "$countones"		{ FL; return yD_COUNTONES; }
   "$dimensions"		{ FL; return yD_DIMENSIONS; }
   "$error"		{ FL; return yD_ERROR; }