diff --git a/Changes b/Changes
index ba11fdaf8..8e37c201e 100644
--- a/Changes
+++ b/Changes
@@ -12,6 +12,8 @@ The contributors that suggested a given feature are shown in []. Thanks!
 
 ****  Fix test problems when missing fst2vcd, bug1417. [Todd Strader]
 
+****  Fix GTKWave register warning, bug1421. [Pieter Kapsenberg]
+
 
 * Verilator 4.012 2019-3-23
 
diff --git a/include/gtkwave/lz4.c b/include/gtkwave/lz4.c
index 5ee034eea..00fbcfca1 100644
--- a/include/gtkwave/lz4.c
+++ b/include/gtkwave/lz4.c
@@ -248,7 +248,7 @@ static const int LZ4_minLength = (MFLIMIT+1);
 /**************************************
 *  Common functions
 **************************************/
-static unsigned LZ4_NbCommonBytes (register size_t val)
+static unsigned LZ4_NbCommonBytes (size_t val)
 {
     if (LZ4_isLittleEndian())
     {