diff --git a/bin/verilator b/bin/verilator
index 2d3c6c538..c0324a0c3 100755
--- a/bin/verilator
+++ b/bin/verilator
@@ -881,7 +881,10 @@ octal (0..) or binary (0b..) notation.
 
 =item Double literals
 
-Double literals must contain a dot (.) and/or an exponent (e).
+Double literals must be one of the following styles:
+  - contains a dot (.) (e.g. 1.23)
+  - contains an expornent (e/E) (e.g. 12e3)
+  - contains p/P for hexadecimal floating point in C99 (e.g. 0x123.ABCp1)
 
 =item Strings
 
diff --git a/src/V3LinkDot.cpp b/src/V3LinkDot.cpp
index 9b080c9c4..a01190964 100644
--- a/src/V3LinkDot.cpp
+++ b/src/V3LinkDot.cpp
@@ -712,13 +712,13 @@ class LinkDotFindVisitor : public AstNVisitor {
     // METHODS
     int debug() { return LinkDotState::debug(); }
 
-    virtual AstConst* parseParamLiteral(FileLine* fl, const string& literal) {
+    AstConst* parseParamLiteral(FileLine* fl, const string& literal) const {
         bool success = false;
         if (literal[0] == '"') {
             // This is a string
             string v = literal.substr(1, literal.find('"', 1) - 1);
             return new AstConst(fl, AstConst::VerilogStringLiteral(), v);
-        } else if ((literal.find('.') != string::npos) || (literal.find('e') != string::npos)) {
+        } else if (literal.find_first_of(".eEpP") != string::npos) {
             // This may be a real
             double v = V3ParseImp::parseDouble(literal.c_str(), literal.length(), &success);
             if (success) return new AstConst(fl, AstConst::RealDouble(), v);
diff --git a/test_regress/t/t_flag_parameter.v b/test_regress/t/t_flag_parameter.v
index 0ac314b7f..33f1c102e 100644
--- a/test_regress/t/t_flag_parameter.v
+++ b/test_regress/t/t_flag_parameter.v
@@ -36,6 +36,10 @@ module t;
    parameter real22 = 0.1;
    parameter real31 = 0.1;
    parameter real32 = 0.1;
+   parameter real41 = 0.1;
+   parameter real42 = 0.1;
+   parameter real51 = 0.1;
+   parameter real52 = 0.1;
 
    parameter int11 = 1;
    parameter int12 = 1;
@@ -63,6 +67,10 @@ module t;
       `check(real22,400);
       `check(real31,20);
       `check(real32,20);
+      `check(real41,582.5);
+      `check(real42,582.5);
+      `check(real51,145.5);
+      `check(real52,145.5);
       `check(int11,16);
       `check(int12,16);
       `check(int21,16);
diff --git a/test_regress/t/t_flag_parameter.vc b/test_regress/t/t_flag_parameter.vc
index 49e71571d..955540440 100644
--- a/test_regress/t/t_flag_parameter.vc
+++ b/test_regress/t/t_flag_parameter.vc
@@ -6,10 +6,14 @@
 -pvalue+string22=\"New\ String\"
 -Greal11=0.2
 -pvalue+real12=0.2
--Greal21=4e2
+-Greal21=4E2
 -pvalue+real22=4e2
 -Greal31=0.2e2
 -pvalue+real32=0.2e2
+-Greal41=0x123.4p1
+-pvalue+real42=0X123.4P1
+-Greal51=0x123p-1
+-pvalue+real52=0X123P-1
 -Gint11=0x10
 -pvalue+int12=0x10
 -Gint21=020