diff --git a/Changes b/Changes
index bc774e2ea..7b1fae7f8 100644
--- a/Changes
+++ b/Changes
@@ -12,7 +12,9 @@ indicates the contributor was also the author of the fix; Thanks!
 
 ***   Support arrayed SystemC I/O pins.  [Christophe Joly]
 
-****  Fix core dump with over 100 deep UNOPTFLAT, bug432.  [Joe Eiler]
+****  Fix expansion of back-slashed escaped macros, bug441. [Alberto Del Rio]
+
+****  Fix core dump with over 100 deep UNOPTFLAT, bug432. [Joe Eiler]
 
 ****  Fix false command not found warning in makefiles. [Ruben Diez]
 
diff --git a/src/V3PreLex.l b/src/V3PreLex.l
index 356491710..241376870 100644
--- a/src/V3PreLex.l
+++ b/src/V3PreLex.l
@@ -81,6 +81,7 @@ quote		[\"]
 tickquote	[`][\"]
 backslash	[\\]
 /* Where we use symb/symbdef, we must also look for a `` join */
+/* Note in the preprocessor \ESCaped is *not* always special; mantis1537/bug441 */
 symb		([a-zA-Z_][a-zA-Z0-9_$]*|\\[^ \t\f\r\n]+)
 symbdef		([a-zA-Z_][a-zA-Z0-9_$]*|\\[^ \t\f\r\n`]+)
 word		[a-zA-Z0-9_]+
diff --git a/src/V3PreProc.cpp b/src/V3PreProc.cpp
index deb5e0dbb..0fae023e0 100644
--- a/src/V3PreProc.cpp
+++ b/src/V3PreProc.cpp
@@ -628,16 +628,18 @@ string V3PreProcImp::defineSubst(V3DefineRef* refp) {
 	string argName;
 	string prev;
 	bool quote = false;
+	bool backslashesc = false;  // In \.....{space} block
 	// Note we go through the loop once more at the NULL end-of-string
 	for (const char* cp=value.c_str(); (*cp) || argName!=""; cp=(*cp?cp+1:cp)) {
-	    //cout << "CH "<<*cp<<"  an "<<argName<<"\n";
-	    if (!quote) {
-		if ( isalpha(*cp) || *cp=='_'
-		     || *cp=='$' // Won't replace system functions, since no $ in argValueByName
-		     || (argName!="" && (isdigit(*cp) || *cp=='$'))) {
-		    argName += *cp;
-		    continue;
-		}
+	    //UINFO(4, "CH "<<*cp<<"  an "<<argName<<endl);
+	    if (!quote && *cp == '\\') { backslashesc = true; }
+	    else if (isspace(*cp)) { backslashesc = false; }
+	    // We don't check for quotes; some simulators expand even inside quotes
+	    if ( isalpha(*cp) || *cp=='_'
+		 || *cp=='$' // Won't replace system functions, since no $ in argValueByName
+		 || (argName!="" && (isdigit(*cp) || *cp=='$'))) {
+		argName += *cp;
+		continue;
 	    }
 	    if (argName != "") {
 		// Found a possible variable substitution
@@ -654,7 +656,11 @@ string V3PreProcImp::defineSubst(V3DefineRef* refp) {
 	    if (!quote) {
 		// Check for `` only after we've detected end-of-argname
 		if (cp[0]=='`' && cp[1]=='`') {
-		    out += "``";   // `` must get removed later, as `FOO```BAR must pre-expand FOO and BAR
+		    if (backslashesc) {
+			// Don't put out the ``, we're forming an escape which will not expand further later
+		    } else {
+			out += "``";   // `` must get removed later, as `FOO```BAR must pre-expand FOO and BAR
+		    }
 		    cp++;
 		    continue;
 		}
@@ -685,12 +691,18 @@ string V3PreProcImp::defineSubst(V3DefineRef* refp) {
 		    continue;
 		}
 	    }
-	    if (cp[0]=='\\' && cp[1]) {
+	    if (cp[0]=='\\' && cp[1]=='\"') {
 		out += cp[0]; // \{any} Put out literal next character
 		out += cp[1];
 		cp++;
 		continue;
 	    }
+	    else if (cp[0]=='\\') {
+		// Normally \{any} would put out literal next character
+		// Instead we allow "`define A(nm) \nm" to expand, per proposed mantis1537
+		out += cp[0];
+		continue;
+	    }
 	    if (*cp=='"') quote=!quote;
 	    if (*cp) out += *cp;
 	}
diff --git a/test_regress/t/t_preproc.out b/test_regress/t/t_preproc.out
index 58bc48252..c78d0844e 100644
--- a/test_regress/t/t_preproc.out
+++ b/test_regress/t/t_preproc.out
@@ -137,7 +137,7 @@ firstline comma","line LLZZ firstline comma","line
 
 `line 71 "t/t_preproc.v" 0
  
-x y LLZZ "a" y
+x y LLZZ "x" y   
 
 `line 74 "t/t_preproc.v" 0
  
@@ -398,7 +398,7 @@ x,y)--bee  submacro has comma paren
  
  
  
-$display("bits %d %d", $bits(foo), `10);
+$display("10 %d %d", $bits(foo), 10);
 
 `line 260 "t/t_preproc.v" 0
  
@@ -709,5 +709,86 @@ module a_b ; endmodule
  
 integer foo;
  
+ 
+module t;
+    
+    
+    
+ 
+ 
 
-`line 457 "t/t_preproc.v" 2
+   initial begin : \`LEX_CAT(a[0],_assignment)  
+`line 464 "t/t_preproc.v" 0
+   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`LEX_CAT(a[0],_assignment) ");   end
+    
+    
+    
+    
+ 
+
+   initial begin : \a[0]_assignment_a[1] 
+`line 471 "t/t_preproc.v" 0
+   $write("GOT%%m='%m' EXP='%s'\n", "t.\\a[0]_assignment_a[1] ");   end
+ 
+    
+ 
+ 
+    
+    
+   initial begin : \`CAT(pp,suffix)   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`CAT(pp,suffix) ");   end
+   
+    
+ 
+ 
+
+    
+   initial begin : \`CAT(ff,bb) 
+`line 485 "t/t_preproc.v" 0
+   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`CAT(ff,bb) ");   end
+   
+    
+ 
+
+    
+   initial begin : \`zzz 
+`line 491 "t/t_preproc.v" 0
+   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`zzz ");   end
+ 
+    
+ 
+ 
+
+    
+   initial begin : \`FOO 
+`line 498 "t/t_preproc.v" 0
+    $write("GOT%%m='%m' OTHER_EXP='%s'\n OUR_EXP='%s'", "t.bar ","t.\\`FOO ");  end
+    
+   initial begin : \xx`FOO 
+`line 500 "t/t_preproc.v" 0
+   $write("GOT%%m='%m' EXP='%s'\n", "t.\\xx`FOO ");  end
+   
+    
+    
+ 
+   initial begin : \`UNKNOWN   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`UNKNOWN ");   end
+    
+    
+ 
+   initial begin : \`DEF_NO_EXPAND   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`DEF_NO_EXPAND ");   end
+ 
+    
+    
+    
+ 
+   initial $write("GOT='%s' EXP='%s'\n", "foo bar baz", "foo bar baz");
+ 
+    
+    
+ 
+ 
+   initial $write("GOT='%s' EXP='%s'\n", "foo `A(bar) baz", "foo `A(bar) baz");
+    
+endmodule
+ 
+
+`line 526 "t/t_preproc.v" 2
diff --git a/test_regress/t/t_preproc.v b/test_regress/t/t_preproc.v
index 022950604..04d7e91ea 100644
--- a/test_regress/t/t_preproc.v
+++ b/test_regress/t/t_preproc.v
@@ -69,7 +69,7 @@ Line_Preproc_Check `__LINE__
 	comma","line)
 
 `define withquote(a, bar) a bar LLZZ "a" bar
-`withquote( x , y)
+`withquote( x , y)  // Simulators disagree here; some substitute "a" others do not
 
 `define noparam (a,b)
 `noparam(a,b)
@@ -254,7 +254,7 @@ Not a \`define
 
 //======================================================================
 // bug191
-`define bug191(bits) $display("bits %d %d", $bits(foo), `bits);
+`define bug191(bits) $display("bits %d %d", $bits(foo), bits);
 `bug191(10)
 
 //======================================================================
@@ -453,3 +453,72 @@ module `Q1 ; endmodule
 // bug311
 integer/*NEED_SPACE*/foo;
 //======================================================================
+// bug441
+module t;
+   //-----
+   // case provided
+   // note this does NOT escape as suggested in the mail
+`define LEX_CAT(lexem1, lexem2) lexem1``lexem2
+`define LEX_ESC(name) \name  \
+
+   initial begin : `LEX_ESC( `LEX_CAT(a[0],_assignment) )   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`LEX_CAT(a[0],_assignment) ");   end
+   //-----
+   // SHOULD(simulator-dependant): Backslash doesn't prevent arguments from
+   // substituting and the \ staying in the expansion
+   // Note space after name is important so when substitute it has ending whitespace
+`define ESC_CAT(name,name2) \name``_assignment_``name2 \
+
+   initial begin : `ESC_CAT( a[0],a[1] )   $write("GOT%%m='%m' EXP='%s'\n", "t.\\a[0]_assignment_a[1] ");   end
+`undef ESC_CAT
+   //-----
+`define CAT(a,b) a``b
+`define ESC(name) \`CAT(name,suffix)
+   // RULE: Ignoring backslash does NOT allow an additional expansion level
+   // (Because ESC gets expanded then the \ has it's normal escape meaning)
+   initial begin : `ESC(pp)   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`CAT(pp,suffix) ");   end
+`undef CAT `undef ESC
+   //-----
+`define CAT(a,b) a``b
+`define ESC(name) \name \
+
+   // Similar to above; \ does not allow expansion after substitution
+   initial begin : `ESC( `CAT(ff,bb) )   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`CAT(ff,bb) ");   end
+`undef CAT `undef ESC
+   //-----
+`define ESC(name) \name \
+
+   // MUST: Unknown macro with backslash escape stays as escaped symbol name
+   initial begin : `ESC( `zzz )   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`zzz ");   end
+`undef ESC
+   //-----
+`define FOO bar
+`define ESC(name) \name \
+
+   // SHOULD(simulator-dependant): Known macro with backslash escape expands
+   initial begin : `ESC( `FOO )    $write("GOT%%m='%m' OTHER_EXP='%s'\n OUR_EXP='%s'", "t.bar ","t.\\`FOO ");  end
+   // SHOULD(simulator-dependant): Prefix breaks the above
+   initial begin : `ESC( xx`FOO )   $write("GOT%%m='%m' EXP='%s'\n", "t.\\xx`FOO ");  end
+`undef FOO `undef ESC
+   //-----
+   // MUST: Unknown macro not under call with backslash escape doesn't expand
+`undef UNKNOWN
+   initial begin : \`UNKNOWN   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`UNKNOWN ");   end
+   //-----
+   // MUST: Unknown macro not under call doesn't expand
+`define DEF_NO_EXPAND  error_dont_expand
+   initial begin : \`DEF_NO_EXPAND   $write("GOT%%m='%m' EXP='%s'\n", "t.\\`DEF_NO_EXPAND ");   end
+`undef DEF_NO_EXPAND
+   //-----
+   // bug441 derivative
+   // SHOULD(simulator-dependant): Quotes doesn't prevent arguments from expanding (like backslashes above)
+`define STR(name) "foo name baz"
+   initial $write("GOT='%s' EXP='%s'\n", `STR(bar), "foo bar baz");
+`undef STR
+   //-----
+   // RULE: Because there are quotes after substituting STR, the `A does NOT expand
+`define STR(name) "foo name baz"
+`define A(name) boo name hiss
+   initial $write("GOT='%s' EXP='%s'\n", `STR(`A(bar)), "foo `A(bar) baz");
+`undef A  `undef STR
+endmodule
+//======================================================================