diff --git a/Changes b/Changes
index 1bcdbcd81..4f92d4afe 100644
--- a/Changes
+++ b/Changes
@@ -12,9 +12,12 @@ indicates the contributor was also the author of the fix; Thanks!
 
 ***   Support bind, to module names only, bug602. [Ed Lander]
 
-***   Fix pin width mismatch error, bug595.  [Alex Solomatnikov]
+***   Define SYSTEMVERILOG, SV_COV_START and other IEEE mandated predefines.
+
+****  Fix pin width mismatch error, bug595.  [Alex Solomatnikov]
+
+****  Fix implicit one bit parameter selection, bug603.  [Jeremy Bennett]
 
-****  Define SYSTEMVERILOG, SV_COV_START and other IEEE mandated predefines.
 
 * Verilator 3.844 2013/01/09
 
diff --git a/src/V3Ast.cpp b/src/V3Ast.cpp
index 9367590b8..f84254154 100644
--- a/src/V3Ast.cpp
+++ b/src/V3Ast.cpp
@@ -1099,6 +1099,10 @@ AstNodeDType* AstNode::findLogicDType(int width, int widthMin, AstNumeric numeri
     return v3Global.rootp()->typeTablep()
 	->findLogicBitDType(fileline(), AstBasicDTypeKwd::LOGIC, width, widthMin, numeric);
 }
+AstNodeDType* AstNode::findLogicRangeDType(VNumRange range, int widthMin, AstNumeric numeric) const {
+    return v3Global.rootp()->typeTablep()
+	->findLogicBitDType(fileline(), AstBasicDTypeKwd::LOGIC, range, widthMin, numeric);
+}
 AstBasicDType* AstNode::findInsertSameDType(AstBasicDType* nodep) {
     return v3Global.rootp()->typeTablep()
 	->findInsertSameDType(nodep);
diff --git a/src/V3Ast.h b/src/V3Ast.h
index 18dc50a1b..b56b48619 100644
--- a/src/V3Ast.h
+++ b/src/V3Ast.h
@@ -551,6 +551,9 @@ struct VNumRange {
     }
     //
     VNumRange() : m_msb(0), m_lsb(0), mu_flags(0) {}
+    VNumRange(int msb, int lsb, bool littleEndian)
+	: m_msb(0), m_lsb(0), mu_flags(0)
+	{ init(msb,lsb,littleEndian); }
     ~VNumRange() {}
     // MEMBERS
     void init(int msb, int lsb, bool littleEndian) {
@@ -1076,6 +1079,7 @@ public:
     AstNodeDType* findUInt64DType()	{ return findBasicDType(AstBasicDTypeKwd::UINT64); }  // Twostate
     AstNodeDType* findBitDType(int width, int widthMin, AstNumeric numeric) const;
     AstNodeDType* findLogicDType(int width, int widthMin, AstNumeric numeric) const;
+    AstNodeDType* findLogicRangeDType(VNumRange range, int widthMin, AstNumeric numeric) const;
     AstNodeDType* findBasicDType(AstBasicDTypeKwd kwd) const;
     AstBasicDType* findInsertSameDType(AstBasicDType* nodep);
 
diff --git a/src/V3AstNodes.cpp b/src/V3AstNodes.cpp
index 734000288..0e465a305 100644
--- a/src/V3AstNodes.cpp
+++ b/src/V3AstNodes.cpp
@@ -557,6 +557,15 @@ AstBasicDType* AstTypeTable::findLogicBitDType(FileLine* fl, AstBasicDTypeKwd kw
     return newp;
 }
 
+AstBasicDType* AstTypeTable::findLogicBitDType(FileLine* fl, AstBasicDTypeKwd kwd,
+					       VNumRange range, int widthMin, AstNumeric numeric) {
+    AstBasicDType* new1p = new AstBasicDType(fl, kwd, numeric, range, widthMin);
+    AstBasicDType* newp = findInsertSameDType(new1p);
+    if (newp != new1p) new1p->deleteTree();
+    else addTypesp(newp);
+    return newp;
+}
+
 AstBasicDType* AstTypeTable::findInsertSameDType(AstBasicDType* nodep) {
     VBasicTypeKey key (nodep->width(), nodep->widthMin(), nodep->numeric(),
 		       nodep->keyword(), nodep->nrange());
diff --git a/src/V3AstNodes.h b/src/V3AstNodes.h
index 98d09db36..8e46ff6b6 100644
--- a/src/V3AstNodes.h
+++ b/src/V3AstNodes.h
@@ -302,6 +302,11 @@ public:
 	: AstNodeDType(fl) {
 	init(kwd, numer, wantwidth, widthmin, NULL);
     }
+    AstBasicDType(FileLine* fl, AstBasicDTypeKwd kwd, AstNumeric numer, VNumRange range, int widthmin)
+	: AstNodeDType(fl) {
+	init(kwd, numer, range.elements(), widthmin, NULL);
+	m.m_nrange = range; // as init() presumes lsb==0, but range.lsb() might not be
+    }
     // See also addRange in verilog.y
 private:
     void init(AstBasicDTypeKwd kwd, AstNumeric numer,
@@ -4482,6 +4487,8 @@ public:
     AstBasicDType* findBasicDType(FileLine* fl, AstBasicDTypeKwd kwd);
     AstBasicDType* findLogicBitDType(FileLine* fl, AstBasicDTypeKwd kwd,
 				     int width, int widthMin, AstNumeric numeric);
+    AstBasicDType* findLogicBitDType(FileLine* fl, AstBasicDTypeKwd kwd,
+				     VNumRange range, int widthMin, AstNumeric numeric);
     AstBasicDType* findInsertSameDType(AstBasicDType* nodep);
     void clearCache();
     void repairCache();
diff --git a/src/V3Width.cpp b/src/V3Width.cpp
index 0a14a5065..9f151b784 100644
--- a/src/V3Width.cpp
+++ b/src/V3Width.cpp
@@ -840,7 +840,17 @@ private:
 			width = 32;
 		    }
 		    // Can't just inherit valuep()->dtypep() as mwidth might not equal width
-		    nodep->dtypeChgWidthSigned(width, nodep->valuep()->widthMin(),issigned);
+		    if (width==1) {
+			// one bit parameter is same as "parameter [0] foo", not "parameter logic foo"
+			// as you can extract "foo[0]" from a parameter but not a wire
+			nodep->dtypeChgWidthSigned(width, nodep->valuep()->widthMin(),issigned);
+			nodep->dtypep(nodep->findLogicRangeDType
+				      (VNumRange(0,0,false),
+				       nodep->valuep()->widthMin(),
+				       issigned?AstNumeric::SIGNED : AstNumeric::UNSIGNED));
+		    } else {
+			nodep->dtypeChgWidthSigned(width, nodep->valuep()->widthMin(),issigned);
+		    }
 		    didchk = true;
 		    nodep->valuep()->iterateAndNext(*this,WidthVP(width,nodep->widthMin(),FINAL).p());
 		}
diff --git a/src/V3WidthSel.cpp b/src/V3WidthSel.cpp
index 7e296e56a..d323be581 100644
--- a/src/V3WidthSel.cpp
+++ b/src/V3WidthSel.cpp
@@ -104,10 +104,7 @@ private:
 			   false); // big endian
 	}
 	else if (AstBasicDType* adtypep = ddtypep->castBasicDType()) {
-	    if (!adtypep->isRanged()) {
-		nodep->v3error("Illegal bit or array select; type does not have a bit range, or bad dimension: type is "
-			       <<errp->prettyName());
-	    } else {
+	    if (adtypep->isRanged()) {
 		if (adtypep->rangep()
 		    && (!adtypep->rangep()->msbp()->castConst()
 			|| !adtypep->rangep()->lsbp()->castConst()))
@@ -115,6 +112,9 @@ private:
 		fromRange.init(adtypep->msb(),
 			       adtypep->lsb(),
 			       adtypep->littleEndian());
+	    } else {
+		nodep->v3error("Illegal bit or array select; type does not have a bit range, or bad dimension: type is "
+			       <<errp->prettyName());
 	    }
 	}
 	else {
diff --git a/test_regress/t/t_param_bit_sel.pl b/test_regress/t/t_param_bit_sel.pl
new file mode 100755
index 000000000..f91289753
--- /dev/null
+++ b/test_regress/t/t_param_bit_sel.pl
@@ -0,0 +1,18 @@
+#!/usr/bin/perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2003 by Wilson Snyder. This program is free software; you can
+# redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+
+compile (
+    );
+
+execute (
+    check_finished=>1,
+    );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_param_bit_sel.v b/test_regress/t/t_param_bit_sel.v
new file mode 100644
index 000000000..f28d56c88
--- /dev/null
+++ b/test_regress/t/t_param_bit_sel.v
@@ -0,0 +1,32 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// We see Verilator assumes a 1-bit parameter is a scalar rather than a 1-bit
+// long vector. This causes the following code to fail.
+//
+// Other event drive simulators accept this.
+//
+// This file ONLY is placed into the Public Domain, for any use,
+// without warranty, 2013 by Jeremy Bennett.
+
+module t (/*AUTOARG*/
+   // Inputs
+   clk
+   );
+   input clk;
+
+   // At this point it is ambiguous whether a is scalar or vector
+   parameter a = 1'b0;
+   wire  b = a[0];
+   // Note however b[0] is illegal.
+
+   always @(posedge clk) begin
+      if (b == 1'b0) begin
+	 $write("*-* All Finished *-*\n");
+	 $finish;
+      end
+      else begin
+	 $stop;
+      end
+   end
+
+endmodule