diff --git a/Changes b/Changes
index 5a47d8f3b..e10aaa4db 100644
--- a/Changes
+++ b/Changes
@@ -14,6 +14,8 @@ indicates the contributor was also the author of the fix; Thanks!
 
 ***  Add --error-limit option.  [Stefan Thiede]
 
+***  Allow __ in cell names by quoting them in C.  [Stefan Thiede]
+
 **** Fix genvar to be signed, so "< 0" works properly.  [Niranjan Prabhu]
 
 **** Fix assignments to inputs inside functions/tasks.  [Patricio Kaplan]
diff --git a/src/V3Ast.cpp b/src/V3Ast.cpp
index 603764760..06d759017 100644
--- a/src/V3Ast.cpp
+++ b/src/V3Ast.cpp
@@ -83,6 +83,20 @@ void AstNode::init() {
     m_user5Cnt = 0;
 }
 
+string AstNode::encodeName(const string& namein) {
+    string name2 = namein;
+    string out;
+    for (string::iterator pos = name2.begin(); pos != name2.end(); pos++) {
+	if (pos[0]=='_' && pos[1]=='_') {
+	    out += "__ULUL_";
+	    pos++;
+	} else {
+	    out += pos[0];
+	}
+    }
+    return out;
+}
+
 string AstNode::shortName() const {
     string pretty = name();
     string::size_type pos;
@@ -114,6 +128,9 @@ string AstNode::prettyName(const string& namein) {
     while ((pos=pretty.find("__PVT__")) != string::npos) {
 	pretty.replace(pos, 7, "");
     }
+    while ((pos=pretty.find("__ULUL_")) != string::npos) {
+	pretty.replace(pos, 7, "");
+    }
     return AstNode::dedotName(pretty);
 }
 
diff --git a/src/V3Ast.h b/src/V3Ast.h
index 42408a567..bc4aed501 100644
--- a/src/V3Ast.h
+++ b/src/V3Ast.h
@@ -558,6 +558,7 @@ public:
     string 	shortName() const;	// Name with __PVT__ removed for concatenating scopes
     static string dedotName(const string& namein);	// Name with dots removed
     static string prettyName(const string& namein);	// Name for printing out to the user
+    static string encodeName(const string& namein);	// Encode user name into internal C representation
     string	prettyName() const { return prettyName(name()); }
     FileLine*	fileline() const { return m_fileline; }
     int		width() const { return m_width; }
diff --git a/src/V3LinkCells.cpp b/src/V3LinkCells.cpp
index d73064dd8..f850830d1 100644
--- a/src/V3LinkCells.cpp
+++ b/src/V3LinkCells.cpp
@@ -127,9 +127,6 @@ private:
 	// Module: Pick up modnames, so we can resolve cells later
 	m_modp = nodep;
 	UINFO(2,"Link Module: "<<nodep<<endl);
-	if (nodep->name().find("__") != string::npos) {
-	    nodep->v3error("Unsupported: Double underscores (__) in module names reserved for internal use: "<<nodep->prettyName());
-	}
 	if (nodep->inLibrary()) {
 	    if (!m_libVertexp) m_libVertexp = new LibraryVertex(&m_graph);
 	    new V3GraphEdge(&m_graph, m_libVertexp, vertex(nodep), 1, false);
diff --git a/src/verilog.l b/src/verilog.l
index a54b5fb18..59b930f84 100644
--- a/src/verilog.l
+++ b/src/verilog.l
@@ -634,14 +634,18 @@ escid	\\[^ \t\f\r\n]+
 			       if (!isalnum(yytext[i]))
 				   yytext[i] = '_';
 			   if (isalpha(yytext[1])) {
-			       yylval.strp = V3Read::newString(yytext+1); // +1 to skip the backslash
+			       yylval.strp = V3Read::newString(
+				   AstNode::encodeName(
+				       string(yytext+1))); // +1 to skip the backslash
 			   } else {
-			       yylval.strp = V3Read::newString(yytext); // Need _ as "6..." isn't legal ID
+			       yylval.strp = V3Read::newString(
+				   AstNode::encodeName(
+				       yytext)); // Need _ as "6..." isn't legal ID
 			   }
 			   return yaID;
 			 }
 
-  {id}			{  yylval.strp = V3Read::newString(yytext);
+  {id}			{  yylval.strp = V3Read::newString(AstNode::encodeName(string(yytext)));
 			   return yaID;
 			 }